On his first day, rookie officer Ben Sherman is assigned to veteran cop John Cooper, his no-nonsense training officer. After being involved in a fatal shooting, Ben already begins questioning his career choice. Detectives Sammy Bryant and Nate Moretta try to convince a young teen to testify after learning she is an eyewitness in the attempted murder of a boy who was mistaken for a gang member. Meanwhile, Detective Lydia Adams investigates the disappearance of a young girl.

An investigation is opened after Ben, John, and Officer Chickie Brown encounter an infant crawling down the street. Lydia takes a personal interest in the case after Child Protective Services gets involved, and goes out on a limb for the mother. Meanwhile, Sammy and Nate are furious when they learn their teenage eyewitness won't get police protection due to lack of funds, and put up their own money after an attempt is made on her life.

Ben and John are called to the home of a man who wants them to find his dog, and another in which a drug overdose led to homicide. Chickie and her partner, Officer Bill "Dewey" Dudek, butt heads after he makes some poor decisions that may have repercussions, and later, Dewey finds himself in an embarrassing situation.

A young Jane Doe found murdered in an alley sets Lydia on an emotional journey, and she discovers her suspect was involved in a cold case. Meanwhile, Sammy's wife, Tammi, decides to embark on a new career, and Nate deals with some family issues and reveals a deep secret.

In an effort to recover Detective Daniel "Sal" Salinger's stolen weapon, Sammy and Nate crack down on the residents in the neighborhood where it occurred. Elsewhere, a man exposes himself to Lydia.

Lydia and her partner, Detective Russell Clarke, investigate a string of jewelry thefts in Bel Air and Ben discovers one of the victims is someone he knows. In another matter, Ben must face his past when it comes back to haunt him. Meanwhile, John reveals a secret he's been harboring for a long time, Russell has troubles at home, and Sammy and Nate take extraordinary steps to protect their eyewitness, Janilla, after another attempt is made on her life.

When Sammy discovers Marta has made bail, and fearing another attempt will be made on Janilla's life, he arranges to have her stay with Lydia, but Janilla's safety is compromised after she visits her old neighborhood. Meanwhile, Sal continues to spy on his daughter's activities, Dewey flips out when Chickie confronts him about his drinking problem, and Russell is caught in the middle when he attempts to defuse an ongoing domestic battle between a neighbor and his wife.

Officer John Cooper clashes with his new boot, Gary Steele, a vet from Afghanistan. Lydia struggles to balance detective work and motherhood. Ben Sherman falls in with a sketchy crowd of cops, while Sammy Bryant is trapped in a hellish custody battle with Tammi.

After Mendoza is injured in a drive-by, Ben takes it upon himself to solve the case, much to Sammy's dismay. Lydia regains her footing as a detective while investigating the murder of a female boxer's husband. Tensions between Cooper and Steele finally come to a head during a traffic stop-gone-sideways.

A breakdown in the LAPD's dispatch system makes a difficult job even harder for the cops, all of whom are already grappling with communication issues. Lydia, in a moment of weakness, reaches out to her old flame, Terrell. John is assigned a new partner; Ben and Sammy's partnership is strained just as Ben makes a romantic connection on the job.

Lydia and Reuben track the killer of a man whose body was slow cooked down to the bone. John and Lucero settle into their new friendship during a day filled with strange calls. Ben and Sammy respond to an insane bank robbery in which the suspects throw cash out into the streets as they make their escape in a getaway car.

John is forced to think about what life will hold for him once he leaves the LAPD. Lydia connects with a man she sent to death row earlier in her career. Much to his chagrin, Sammy becomes a tabloid celebrity for the day after a very public act of heroism. Ben makes a dubious decision to get a drug dealer arrested. And a foot pursuit puts Dewey in danger.

The day’s events bring all of our cops face to face with some of their greatest fears. The death of a baby shakes Lydia to her core. Sammy is questioned by I.A. about his altercation with Tammi. A difficult day on the job causes Cooper to seek solace in Hicks but finds none. Ben becomes more deeply involved with Brooke while continuing to see Elena.

John takes drastic measures to try to save Hicks while being confronted with demons from his past. Sammy’s lie about the tape weighs heavily on his conscious. Lydia and Ruben track down a John Doe. Ben’s relationship with Elena becomes more serious.

The funeral of a major drug dealer brings gangsters of all kinds out of the woodwork, there is chaos in the streets but as our cops learn sometimes the greatest threats come from within. Lydia and Ruben investigate the drug related murder of Sgt. Hill’s son; they discover police corruption in the process and clash over how to handle it. Ben suspects that Sammy did not destroy the tape and decides to take matters into his own hands with tragic consequences. John sinks farther into his loneliness.

Chaos prevails in the city of angels when Cooper and Lucero are kidnapped and held hostage by a pair of tweakers. All of our cops join the frantic search to find their brothers in blue before it is too late. Sammy searches for Strokeface. Ben tries to throw Sammy off the trail while simultaneously dealing with an increasingly irrational Brooke.

John copes with the aftermath of his kidnapping. Sammy closes in on the real robbers. Lydia continues to pursue John’s kidnappers and becomes more intimate with Russell.