Bosco, Yokas, Sully and Davis search for a cop killer on the streets, and cope with an obnoxious new sergeant at the station house.

Faith, Bosco, Carlos and a wounded Doc find themselves trapped in an abandoned tunnel and unable to reach Central on their radios; the firefighters get into mischief during a long lull between calls; when the C.O. can't raise Bosco on the radio, Sully tries to cover for him.

Faith and Bosco hunt down the dealer who distributed a batch of lethal heroin; depressed over Bobby's death, Kim attempts suicide.

The police officers sort through the carnage and count their dead in the wake of a shootout between rival gangs. While Faith tries to interrogate Fyodor Chevchenko, a ruthless Russian mobster, Sully worries about the severely wounded Ty and regrets causing the incident. Tatiana chastises Sully for hassling her injured son. Faith worries about Gusler, her ineffective, frightened rookie partner, and a weary Doc gets some unexpected good news about his medical malpractice suit.

During the investigation of the gang shootout, the officers are questioned and presented with evidence which suggests that Ross was killed by friendly fire; Carlos learns that Vangie is dead and that he might be the father of the baby her sister leaves at the firehouse; on the first anniversary of Bobby's death, Kim quarrels with Jimmy over her visitation with Joey and confronts a female gang during a call; and Doc is visited by the father of a former patient whose debilitating injury may have been caused by Doc's error during treatment.

Bosco's emotional turmoil escalates when he begins to experience panic attacks and flashbacks, but continues to deny that there's anything wrong. After he has a panic attack while driving the patrol car and nearly causes a crash, Sully insists that Bosco see his friend Brian O'Malley, who's a therapist and a former cop.

Hopelessly in love with Kylie and concerned that she will lose her Latina heritage if she is adopted by a white couple, Carlos considers raising her until he realizes that the couple can give her the sister, the grandparents, and the extended family that he cannot; Kim's preoccupation with her new PDA drives Alex crazy until they are able to use it to save a very sick man, thus redeeming themselves in the eyes of a hypercritical Dr. Peterson; Faith and Fred are still on uneven ground about the sergeant's exam; in an effort to shake Chevchenko's tree, Faith and Sully execute a clever plan to disrupt the Russian's bookmaking operation, which also opens the door to the possibility of the still-missing Tatiana's return; Bosco is cleared for duty, and he and Faith agree to be partners again as soon as he returns.

Hopelessly in love with Kylie and concerned that she will lose her Latina heritage if she is adopted by a white couple, Carlos considers raising her until he realizes that the couple can give her the sister, the grandparents, and the extended family that he cannot; Kim's preoccupation with her new PDA drives Alex crazy until they are able to use it to save a very sick man, thus redeeming themselves in the eyes of a hypercritical Dr. Peterson; Faith and Fred are still on uneven ground about the sergeant's exam; in an effort to shake Chevchenko's tree, Faith and Sully execute a clever plan to disrupt the Russian's bookmaking operation, which also opens the door to the possibility of the still-missing Tatiana's return; Bosco is cleared for duty, and he and Faith agree to be partners again as soon as he returns.

Rescuers find the body of Alex's father, and he is given a hero's burial; Faith and Bosco tail a convicted rapist released on appeal, certain that he will rape again; dissatisfied by Tatiana's explanation of her whereabouts the eight weeks she was missing, Sully investigates further and uncovers some astonishing and heartbreaking facts about his wife; after Chevchenko threatens to kill him if he doesn't roll over on Faith and Sully, Frankie tells Swersky that the raid on Chevchenko's numbers business was a hummer bust, leading Chevchenko to threaten a lawsuit and have another angry confrontation with Sully.

When a blackout strikes the city during a heat wave, Sully prophetically warns the more optimistic Ty that trouble in the streets will swiftly ensue. After Carlos leaves the ambulance running to keep the bus cool while he and Doc are on calls, the engine catches fire and the ambulance is destroyed. A wealthy old man confined to his bed by illness offers them a large amount of money to stay with him until his daughter arrives. Doc insists that they leave to treat others more in need over the protests of Carlos. Bosco arrests a young man, Latrell Griffith, and faces a difficult decision when an immigrant shop owner shoots and wounds a teenage shoplifter. After Latrell uses his training as a medic to save the boy, a riot breaks out and Bosco, Latrell and the shoplifter barely escape. Nightfall brings more unrest as the nervous cops try to keep the peace. Faith and Fred are stuck in a elevator when the power goes out. Faith tries to calm Fred's mounting anxiety about being trapped, and is

Bosco gets a temporary assignment working with a tough female sergeant; Fred is strangely calm in the face of the prospect of a triple bypass; Doc hears shocking news from Philadelphia; Sully learns more about Tatiana's past; Davis is forced to deal with his newfound fame.

Yokas and Bosco try to find a missing boy whose parents think has been taken by a registered sex offender; Sully prepares to be questioned about his wife's background

Chevchenko has Tatiana's son killed; Fred comes home from the hospital; and Davis gets a job offer.

Chevchenko has Tatiana's son killed; Fred comes home from the hospital; and Davis gets a job offer.

Emily discovers just what Faith's job entails and how much her mother loves her when they are taken hostage during a bank robbery, and Faith risks her life to save her daughter.

Monty and Joy hook up. Miguel witnesses one drug dealer murder another, and becomes the dealer's next target. On his first day back at work, Sully rides with Faith, who is put off by his short fuse and bad attitude. When he leaves a prisoner unguarded and uncuffed, Faith tells him to go home because he's not ready to be back on the job. Sully gets drunk and goes to his mother's nursing home. Sobbing about Tatiana, he tries to batter down the door when the receptionist won't let him in and calls the police. After Hancock arrives on the scene, Sully mouths off to him about Nancy in front of the other officers who are there to take him home.

Bosco is dismayed as he watches Cruz go to the extreme lengths of planting drugs, frightening children, and faking a dying declaration in their attempt to arrest the drug dealer who killed another dealer and then tried to to kill the 12 year old boy who witnessed the crime; Nancy tells Ty that she's ending her relationship with Hancock, and gives Ty the ammunition he needs to get out from under Hancock's thumb and back to duty at the 55, as well as getting Sully's suspension from duty lifted.

Doc supervises a new paramedic on her first day; Carlos is arrested after a teenaged patient accuses him of molesting her; Bosco and Faith search for an escaped prisoner; Sully and Davis team up with fire and EMS to save construction workers when their scaffold collapses; in the aftermath of the bank robbery, Faith is troubled when Emily asks her how many people she's killed in the line of duty.

Sully's stopped drinking, but his poor attitude remains; Carlos gives his two week notice; a blizzard blankets the city and the squads are called in early; an understaffed Doc defies orders and puts Carlos back on the street as the squads are kept busy rescuing victims of the storm; Faith's initial wariness about Emily's new boyfriend Eric turns out to be well-founded when he is brought into Mercy after an overdose of Special K, but doesn't remember where he left Emily after she also got high; Faith, Bosco, Sully, Ty, Doc and Carlos go out to search for Emily, and rush her to Mercy after she's found in critical condition; Faith and Fred blame each other for letting Emily go out with Eric.

As she keeps vigil by Emily's bedside, Faith recalls her first days at the Police Academy and the beginning of her friendship with Bosco; the fire squad rescues Bosco, Maritza, and a very pregnant Linda Barnes from the inferno, but Lettie Cruz succumbs to her drug binge before they can reach her; Emily is released from the hospital and takes responsibility for her overdose; Bosco tracks down Gary Barnes with Linda's help; Maritza and Bosco's relationship goes to a new level when he attempts to comfort her on the lost of her sister; Kim finally testifies before the review board and stands up for Carlos.

Sully hits bottom when Ty washes his hands of the partnership after Sully's drinking goes completely out of control; a thief strikes fear in the hearts of the police when he phones in false ""officer-in-need-of-assistance"" calls to cover his fur store robberies; Faith and Maritza go at it after Maritza's lonesome cowboy tactics nearly get another cop killed, and Faith is forced to shoot a perp to save Maritza's life after she goes after the perp without backup; Doc has an unpleasant encounter with Joy's father; Faith is disgusted when she finds out about Bosco and Maritza, and Maritza confirms that she put Bosco in front of a lie about a dying declaration to obtain a conviction on a drug dealer; Ty overcompensates for Sully's inattention to the job by becoming a ""supercop"" with an eye to getting a gold shield.

Sully is sober and back on the job; Faith continues to keep a close watch on Emily; a mutual attraction springs up between Kim and a reporter; Faith and Bosco pursue a man after he steals a bag of money from an overturned armored car involved in a fatal accident; Faith is unable to dissuade Bosco from wanting to hide the cash after the robber drops it, rather than carrying such a heavy load during a foot chase, and is proved right when they return later to retrieve the bag and find that it's been stolen yet again; faced with disciplinary action and investigations by the Major Case Squad and IAB, they pound the pavement trying to find the second perp and discover that the accident with the armored car had been staged by one of the guards and his girlfriend; Maritza ends up stealing the first perp's collar from Faith, which further erodes their relationship; Bosco is jealous when the Major Case Squad detective running the investigation turns out to be Maritza's former boyfriend; as Doc and Kim rush Nicole West to Mercy after a suicide attempt, she tells Kim that her stepfather Anthony has been molesting her; when Nicole's mother refuses to believe that her husband has done anything wrong, Kim implores Melinda to see that her daughter is crying out for help with repeated suicide attempts; after Nicole convinces Melinda that Anthony is guilty and reveals that her accusations against Carlos were false, Melinda apologizes and withdraws her complaint against Carlos and the city; still at odds over trust and honesty issues, Faith and Bosco trade painfully honest barbs and decide to split up; Carlos is elated when Ty tells him he's being reinstated.

Kim is invited to a party by Noble. Noble is arrested through an undercover operation. He becomes an informant and helps Cruz and Bosco bust a Meth ring. Faith officially requests a new partner. Emily and Faith face off about Eric.

Cruz's desire to find the ring leader of the Meth ring puts Bosco in a uncomfotable position. Faith tries to improve her relationship with Emily and also gets a new partner, Sasha, at work. Noble is released and sets up a new date with Kim.

Maritza's reckless pursuit of Buford triggers a horrific car accident that leads to multiple injuries to motorists, and triggers an explosion that severely injures Lt. Johnson and kills Alex Taylor; Doc and Kim get to the top of the promotion list; Maritza hangs Bosco and Nunez out to dry over the murder Noble committed; Doc's overwhelming guilt and grief over Alex's death leads him to a career decision; Maritza discovers that Faith has agreed to help Bosco clear Nunez by getting Noble's gun, and goes to Noble's place to intercept her, followed by Bosco and Noble; when Bosco insists on arresting Noble and Faith refuses to turn over the gun, Maritza draws on Faith, Bosco and Faith draw on Maritza, and three shots ring out.

Although Dade encourages him to keep quiet, Bosco tells Swersky everything that transpired with Maritza, Noble, the death of Willie G, and the shootout in Noble's hotel room, and confesses that he killed Noble after Noble pulled out a gun, Faith was shot by Maritza, and that he grazed Maritza's head with a bullet to keep her from killing Faith; wracked with grief that his wife has a bullet next to her spine, Fred attacks Bosco and threatens to kill him when he discovers that Faith became injured while she was helping her partner out of yet another jam; a critically injured Lt. Johnson, in excruciating pain and with only hours to live, begs Jimmy and Doc to ease his suffering; overwhelmed at the sight of Lt. Johnson's wife lashing out in heartbreak and anger, and her husband's horrific suffering and imminent death, Doc sadly helps out his boss one last time; Swersky has Maritza arrested when she refuses to tell him what happened during the shootout; Bosco learns that Noble was working f

On his last day on the street, Doc's guilt and grief over Alex's death emerges as anger towards everyone he encounters, especially Eugene, the new paramedic trainee whose place Alex took the day she died; Kim becomes frantic as she fears that she have been exposed to HIV after having unprotected sex with a drug addicted Noble, and Jimmy agrees to accompany her when she gets tested; Swersky goes to bat for Faith by creating the opportunity for Bosco to talk to her before she's interrogated by I.A.B.; Carlos is less than thrilled when he discovers that Kim is the new supervising paramedic and Jimmy has been promoted to take over Lt. Johnson's position; Bosco returns to work and faces a hostile reception from the squad for ratting out Maritza; Faith awakes to discover that she's paralyzed; Maritza refuses to let Faith off the hook for shooting her until Bosco tricks her into recanting her story; Faith thanks Bosco for keeping her out of jail and saving her job, and then tells him to get l

Yokas clashes with her mother over her recovery; Maritza is back on the job, but unhappy that she's back in the bag and handing out parking tickets; Ty and Sully discover a truck carrying sick illegal aliens and end up scouring the city to track down one of them who escapes after it's determined that the aliens have a highly contagious and potentially fatal disease.

Sasha, Bosco, Sully and Ty get on the case of a malicious rapper. Ty considers returning to law school with the help of Sully. Jimmy struggles with his new position and his relationship with his co-workers when he makes a big mistake during a fire drill. Faith gets a physical therapist.

Over her protests, a judge marked for execution is placed under a protective detail and gives Sully and Ty a scare when she slips away to get a cup of coffee; Levine uses an unorthodox way to get a patient's mind off his pain; when no physical reason can be found for Faith's intense pain, her doctor refers her to a psychiatrist; Kim is livid when Doc gives her an official letter of reprimand for disregarding field regulations just the way he did several times; in an effort to get out of the bag and off the street, Maritza convinces Swersky to let her set up a sting operation to catch a chiropractor who's fronting for prostitution, and pays a terrible price for continuing her ""lonesome cowboy"" approach to apprehending criminals.

Barbara is heartbroken when she discovers that her housekeeper was killed by the explosion; Sasha convinces Maritza to get a rape exam; Sully takes Barbara to his house to keep her safe; Maritza discovers that her rapist, Thomas Warner, has a history of sexually assaulting the workers at the clinic; undeterred by yet another attack on her life, this time by a sniper, Barbara insists on presiding at the preliminary hearing of Gary Barnes, the drug dealer who the police suspect is behind the attempts on her life; Faith visits a psychiatrist and unloads her anger at Bosco and Maritza; after Maritza testifies at the hearing, Barbara rules that Barnes can be held over for trial for the death of Lettie Cruz; when Sully sees Barnes signal a spectator in the court room, he and Ty follow him to a house where they see him join the man who delivered the bomb to Barbara's house; the perps, armed with a detonator, threaten to blow up the block with the explosives they claim are in the house and for

Sully kills one of the perps and shoots the denotator out of the hand of Frank Morgan, the bomber; Doc goes ballistic when he comes upon the scene of an accident involving his old rig and a city bus, and physically assaults Eugene; Public Morals raids Dr. Chow's office, and Maritza is forced to reveal her rape to keep Thomas Warner from being released on a D.A.T.; Ty gets Frank Morgan to flip on Gary Barnes, and Barbara promises Morgan that she will make sure he gets the death penalty for killing her housekeeper and driver; Kim and Carlos refuse to back up Eugene after he files a complaint against Doc, prompting Eugene to quit; a distraught Faith, still plagued by flashbacks of the shooting, asks Fred if they can get out of the city for a family vacation; Warner confesses to raping Maritza while Bosco is transporting him to the Tombs; Carlos is horrified when Doc admits that he accosted Eugene at his house because he ""killed Taylor""; Bosco turns Warner over to Maritza, who gets her pay

Doc is demoted back to the streets and continues his downward spiral, presenting Kim with no end of problems as he lies about his demotion, resists her orders as the supervising paramedic, and deliberately runs down a perp with the bus; Barnes is shanked at Riker's for doing a flip on Buford; Carlos is devastated when Kylie is diagnosed with aplastic anemia and he's not a match for a bone marrow donation; Sully tries to deflect Ty's teasing about his relationship with Barbara by getting him to focus on their LSAT prep; after a horrific gunfight, Maritza finally captures Lettie's killer and decides to spare him so that he can suffer for the rest of his life in prison.

As Carlos desperately searches for a bone marrow match for Kylie, he digs deeper into his own past and discovers that he wasn't abandoned by his parents, but was found clinging to his dead father's hand after a car accident; after a local station picks up the story, Carlos gets a call from a woman claiming to be his mother; Bosco and Monroe find themselves going after a small-time mobster putting the squeeze on an honest family-run linen company after the son of the linen company owner dies in a suspicious fire.

Bosco arrests a pedophile posing as a toy store Santa, and the grateful store owner returns the favor by helping Bosco and Sasha come to the aid of a man whose house is robbed of all his children's Christmas presents; after Sully and Ty save a young homeless girl from a fire, she rekindles Sully's Christmas spirit; Carlos receives the ultimate Christmas present when his brother arrives at the firehouse bearing the gift of being a perfect bone marrow match for Kylie, as well as the news of Carlos's real name and family history; Kim and Jimmy spend a romantic Christmas Eve together; Sasha's search for the perfect gift for her nephew gives Swersky the opportunity to play Santa.

When Sasha discusses taking the sergeant's exam with Maritza, Maritza reveals that she received her promotion meritoriously, not from passing the test; the police are on high alert after two women are assaulted and robbed by men posing as police officers; Kim and Jimmy decide to keep their blossoming romance quiet until Kim is pulled over by the impostors and narrowly escapes with her life with the help of Bosco, Maritza, Sully and Sasha.

Jimmy gets a promotion to a rescue squad in Brooklyn; despite their new captain's assurances, Doc suspects that he intends to close down the house; Sasha insists upon pursuing an investigation into the beating death of a hit-and-run driver after Maritza uses the confession of an innocent man as her stepping stone to an Anti-Crime reassignment; after Jimmy is trapped in a warehouse fire, Kim reassesses their plans for a future together; Rose's serves a customer at the bar who shares a past with Bosco.

Steeper exiles the paramedics to permanent fixed posts on the street, which upsets everyone on the squad except Doc, who refuses to let anything put a damper on his unusually upbeat attitude; Carlos is less than thrilled when Doc invites Christian to accompany them on a ride-along without getting the proper authorization; when Bosco goes after Nardo for his veiled threats against Rose, Nardo tries to set Bosco up to look like a dirty cop; Rose is fired after Bosco destroys poker machines owned by Nardo in the bar where she works; on the eve of her return to duty, Faith tells Bosco that she wants to repartner with him; Sasha's second thoughts about the plan she and Bosco hatched to repay Nardo for threatening Rose and attempting to frame Bosco turn out to be on target when Nardo flees after murdering two men; Doc and Sasha hook up after Doc throws a big party at his house for his co-workers.

Steeper continues his by-the-books command style and goes head-to-head with Kim when Doc doesn't report for duty on time; Sasha can't find her off-duty weapon the morning after Doc's party; Faith returns to duty at the front desk despite Fred's wanting her to remain on disability, and discovers that Bosco has lied to her about Swersky's not allowing them to be partners; a panicky Nardo kidnaps Rose and then Bosco in a futile attempt to prove that he wasn't a rat, and makes a shocking choice when he realizes that his days as a mobster have come to an end; to the horror of the squads, Doc takes extreme measures to prevent Steeper from closing the house, and forces Carlos and Kim to risk their lives to do the right thing; Sully returns a favor by reaching out and saving his friend's life in Doc's hour of greatest need.

The news that Faith is repartnering with Bosco outrages Fred; Bosco overcomes his initial wariness about his brother's claims of sobriety after the tip Mikey gives him about Ecstasy dealers leads to a solid bust; in the wake of the hostage situation, the department shrink sent to debrief the house elicits a range of emotional reactions from Kim, Carlos and Holly as she reveals that Doc is in the Bellevue psych ward on a suicide watch, and that the toll of 9/11 and its aftermath may be at the root of his collapse; when she investigates the murder of an Ecstasy dealer outside a rave, Maritza discovers that the motive may be a turf war between rival dealers; Bosco is distraught when Maritza informs him that the evidence points to Mikey's being a major Ecstasy dealer who used him to eliminate the competition by providing the tip that lead to the raid; Bosco and Maritza set out separately to find Mikey; tragedy occurs when Maritza and Dade pull over Mikey's car outside a rave.

Maritza goes all out on the hunt for Michael after Dade dies, as does Bosco, who's intent on finding his brother before Maritza does; Faith calls Maritza a liar in front of Swersky when Maritza claims that she saw Michael shoot Dade; Fred is still angry about Faith repartnering with Bosco, and refuses to discuss it; Breene revisits the house and urges the paramedics to talk to professionals or to each other to help deal with the stress of the shootout; looking to collect the reward for information leading to Dade's killer, Anthony tells Maritza where Michael can be found after she lies to him about her relationship with Bosco; Bosco finds Michael moments before Maritza, and his brother claims that he's innocent and that a drug dealer named Spider was Dade's murderer; Spider comes out with machine guns blazing when Maritza, Sully, Ty, Faith and Bosco attempt to arrest him, and a ferocious gun battle ensues; Maritza agrees to work with Michael as an informant after Bosco pleads for his

Distraught over losing an appeal to her suspension, Sasha gets into a car accident that claims the life of a young child; Sully and Ty take the L.S.A.T.; tensions flare between the cops and the firefighters when Maritza goes after J.D., the newbie firefighter, who turns out to be an ex-cop who ratted out Maritza's former partner for stealing drug money; Faith and Fred are still at odds over her return to work; Walsh is promoted to lieutenant; Ty watches over a devastated Sasha, who's racked with guilt over the car accident, Doc's shooting spree, and the events surrounding the deaths of Tanzi and Nardo; J.D. gives Faith and Bosco important evidence he discovered as he put out the fire resulting from Sasha's car accident, which leads the cops to uncovering the basis for the accident and exonerating Sasha.

Wary of Lester Martin, the high-priced lawyer his father has found for Mikey and the deal he's attempting to broker, Bosco warns his brother to stay away from Maritza, but Mikey decides to disregard his brother's advice and makes a deal to become her informant; for good measure, Bosco threatens to kill Maritza if anything happens to Mikey; Sully teases Ty about his budding relationship with Sasha; Faith and Bosco strike a deal with Laura, who also has no love lost for Maritza, to protect Mikey by helping her nab the drug dealers before Maritza gets to them; J.D. offers Kim a ride home, but stops off first at a rave that both Anti-Crime and Narcotics have staked out, thanks to information Mikey gave them; when some bad ecstasy begins to take a rapid toll, the paramedics call for backup, which prompts Maritza and her detail to storm the building; after an arsonist lobs a Molotov cocktail into the crowded building, Faith and Bosco give chase and capture him, while the firefighters rescue

Tensions still run high in the Yokas household; Lester preps Bosco for Mikey's hearing, and then pulls a switch when he cross-examines him on the stand, leading to Mikey's getting RORd; Sully realizes what a toll the job has taken on him by his reaction to the deaths of three people in a robbery at the restaurant where he eats breakfast every day; Faith and Bosco answer a call which leads them to Lester's house, where they find his daughter not breathing; Sully tracks down and arrests the restaurant murderer; after Dr. Hickman tells Faith and Bosco that Lester's wife and daughter have been severely beaten, Lester is arrested; Sully gets his LSAT results; Ty and Sasha get closer.

The Boscorelli family suffers a tragic loss at the hands of Donald Mann, who blames Bosco, Faith and Maritza for the death of his son in a high-speed chase; the Yokas family heads off in different directions; the Martin family splits apart into separate jail cells for the parents, and a return home for Rebecca to the mother from whom she was stolen as an infant; the paramedic family at the 55 gets a new member, Grace Foster, which makes no one involved very happy.

Faith begs Fred to return home, but he refuses for a reason that infuriates his wife; Bosco turns a cold shoulder to Maritza's attempts to offer her condolences; Carlos is spectacularly unsuccessful in his attempts to hit on Grace; on the day of his son's funeral, Donald Mann exacts his revenge with the help of a dirty cop by planting bombs designed to kill the police officers he holds responsible for the death of his son; after Mann's lieutenants force a man to crash a car carrying a live bomb into the funeral home where Mikey's wake is being held, Grace takes charge and goes out of protocol to save Rose's life, and Dr. Fields later swears to have her job for it; Kim's decision not to enter the funeral home while the bomb is still live stems not from cowardice, but from maternal instincts; when Mann discovers that some of his intended targets survived the bombings, he sends machine-gun wielding minions into the hospital to finish off the job.

After a fierce gun battle and some hand-to-hand combat, Mann's gunmen are finally subdued by the members of the 55 in the E.R., but not before Orland is murdered and Bosco is critically injured; after Kim heroically puts herself in the line of fire to save Holly and a little girl, she realizes that her days as a paramedic are over, and that her future lies in being a wife to Jimmy and a mother to their children; Grace and Dr. Fields patch up their differences and come to an understanding about her out-of-protocol field procedures; Maritza uncovers the traitor in their midst, who leads her to Mann; Faith steps over the line to avenge her partner.

After she realizes that telling the truth will mean and prison sentence and never seeing her children again, Faith reluctantly agrees to go along with Maritza's cover story that she shot Mann as he was trying to stab Maritza; Yoshi slips out of the cuffs and into the wind; Sasha and Ty hook up; Maritza gets a tough new boss who's been charged with keeping her on a very short leash to curb her renegade ways; Faith goes ballistic when Fred has her served her with divorce papers at the station house; Swersky shuffles the partnerships, and assigns Faith to ride with Sully and Sasha to ride with Ty; Maritza gets an anonymous call that there's an I.A.B. plant in the house who's after her, and she immediately suspects that it's her new boss; Faith decides to turn down the promotion to detective that she's offered for saving Maritza's life until Sully reminds her that the new assignment will improve her chances of getting custody of her children; Bosco's surgeon gives Faith a devastating progn

Finney continues to press an increasingly reluctant Sasha for information on Faith; Carlos gets nowhere trying to put the moves on Grace; Ty gets promoted to a Field Training Officer and is forced to contend with Brendan, an impulsive and hot headed new police officer who also happens to be Finney's son; after Faith is unsuccessful in getting any of her family members to attend her promotion ceremony, a wired Sasha takes her out for a drink afterward and tries to engage her in conversation about Mann's death; after complaining of boredom, Brendan is forced to watch in horror as a woman is broadsided by two different cars in a terrible car accident; Carlos is spooked after he suffers a series of minor mishaps in the wake of an irate fortune teller's putting a curse on him, and Grace has a little fun with him when she takes full advantage of the situation; Sully tells everyone who'll listen that Finney is a corrupt cop, and that his son doesn't belong in their squad; Holly does a ritual

Faith gets an earful from her daughter for not being around, and discovers that Emily's decision not to attend her mother's promotion ceremony was calculated to drive home a point about all the events Faith missed over the years; Finney threatens to blow Sasha's cover if she doesn't get the goods on Maritza; Sully and Sasha get more than they bargained for when they investigate a domestic and discover a decomposing corpse in the apartment directly above the quarreling couple, leading Sully to teach Brendan a lesson about the less glamorous aspects of police work; starting her career as a detective by partnering up with Jelly, Faith pursues her hunch that there's something more to what appears to be a simple suicide, and uncovers the deceased's plan to commit murder with a mail bomb; Grace teases Carlos about dating Holly, while expressing some interest in Brendan; Ty tries and fails to get more information from an uncooperative Sully after Brendan tells Ty that their fathers and Sully

When it becomes apparent that the body in the dumpster is connected to a series of homicides that Miller investigated on his previous tour, he teams up with Faith, vowing to catch the serial killer and expose the commanding officer who transferred him to prevent him from working on the case; Brendan and Grace hook up; Carlos's plan to visit Holly and tell her that they're not dating doesn't exactly go the way he planned, not that he's complaining; after junkies trying to get the morphine on the bus hold them up at gunpoint, Carlos sustains a head injury trying to protect Grace before Ty and Brendan come upon the scene and Brendan guns down the thief holding a gun to Grace's head; Faith discovers that Miller's situation at home parallels her own; the serial killer stalks and captures his next victim, then arrives at the station house to confess his prior crimes and tell Miller that his latest victim only has twelve hours left to live.

Miller goes on the hunt for Tara Connelly, and Faith tries a series of approaches to get Barton to reveal the girl's whereabouts, until Miller returns to finish off the con that gets Barton to give it up; although they're both still shaken up by the shooting, neither Brendan nor Grace is willing to discuss it or get some counseling; Finney makes sure that his son's shoot comes up clean in the IAB investigation; at Sasha's house, a picture of the knife that Maritza planted on Mann accidentally falls into Ty's hands, but he doesn't realize the implication of his find; over his protests, Carlos gets admitted into Mercy for overnight observation of his head injury, with Holly vowing to stay by his side; a guilty Faith looks on as Finney arrests Maritza for Mann's murder

Maritza calls on her own experience to persuade a rape victim to identify his attacker and sign a complaint after she collars the perp and gets a confession; Ty's prison visit to his father's killer has devastating consequences for both of them; Faith frantically searches for her son when Fred's girlfriend reports that he's missing; the former partners come to blows after Ty accuses Sully of being part of the cover up in the death of Ty's father; both Ty and Sasha deny telling I.A.B. about the knife when Maritza questions them; Sasha uncovers further details about the conspiracy to murder Ty's father and the ensuing cover up.

Sasha anonymously slips Ty the I.A.B. file on the cover up of his father's death; Faith visits Bosco and lets him know how much she misses having him for a partner; Sully bristles at being partnered with Brendan; Faith learns a hard lesson about good detective work when she lets herself get hoodwinked into acting on prejudice and ill-informed assumptions in arresting an innocent man for the death of a pregnant Muslim teenager; Brendan and Grace decide to start over and take their relationship along slowly; after Ty reaches out to exactly the wrong person in the department's top brass to uncover the truth behind his father's death, Finney sets the stage for letting Ty know about Sasha's I.A.B. assignment and threatens them both if they continue with their investigations; Fred gets custody of Charlie and Emily agrees to live with Faith; Sully pursues his options on coming forward about Ty Sr.'s death; Brendan once again single-handedly rushes to the rescue to prevent a suicide.

Ty rats out Sasha to the squad after Finney refuses to transfer her out; an action star doing research for his next movie goes on a ride along with the firefighters, and Stu quickly discovers that his boyhood hero is a failing alcoholic looking for a chance to revive a dead career; Brendan offers to ride with Sasha when everyone else refuses to do so, which leaves Ty and Sully partnered again; the retired detective who gave Sasha the real I.A.B. file on the death of Ty's father is found murdered by a police-issued bullet; Sully decides to testify against Finney; in pursuit of a drug dealer who shot an eight year old girl, Sasha and Brendan are injured, but the other units in the sector fail to respond to their calls for help until Ty and Sully finally relent and come to their aid.

Everyone in the 55th Precinct faces their worst fears when terrorists are discovered to possibly be building a dirty bomb. Carlos and Levine face trouble in their relationship. Captain Finney decides to end his life, rather than surrender himself for the murder of Ty Davis Sr. Brendan and Davis try to cover it up.

Cruz teams up with Rice to track down the terrorists associated with the possible dirty bomb.

Finney gets a frantic phone call from Ben, a child he had helped in a previous case, which said that Ben's father was hurting Ben's mother and coming after Ben. Ben's father takes him to an abandoned warehouse, where the police soon follow.

After a suspect in a jewelry store robbery starts displaying symptoms of a disease similar to SARS, the NIH is called in to figure out what is causing this, and hopefully stop this epidemic. Meanwhile, Cruz faces off with a gangbanger, who may have hired a 13 year old boy to carry out a murder.

The crossover continues on Medical Investigation S01E17 Half Life (II)

Cruz connects the dots that link Marcel Hollis to the murder of Darren Maddox, while Marcel begins to organize a street war against the 55th Precinct. Elsewhere, Yokas, Sully, and Bosco track a missing teen to a vampire cult.

Monroe and Bosco deal with an angry mother on welfare who shoots up the welfare office, Davis and Finney stake out a man and take down a prostitution ring, Faith deals with Emily, Cruz and Monroe recieve bad news about their health.

Faith investigates Bosco further, Sasha and Ty make up, Cruz goes for some spiritual healing, Carlos meets Holly's parents.

Finney and Davis are seriously injured in a car accident during a traffic jam, which was caused by a man trying to kill two people, and he succeeds. Emily's life is in danger when she falls in with the wrong crowd. Carlos buys an engagement ring for Holly.

Faith negotiates the end of a live on TV hostage situation. The leader of a vampire cult holds Emily hostage until Bosco saves the day. Cruz attempts to negotiate a deal with a gangbanger to end the war on the 55th Precinct, but instead, he organizes his troops to attack.