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.

When a fire breaks out in the supermarket where Bosco and his mother Rose are doing some late night shopping, Bosco rescues most of the shoppers but cannot save a young mother when she goes back inside to retrieve her purse. After Jimmy tells him that the fire was probably deliberately set, Bosco is convinced that he saw the arsonist in the crowd outside after the fire. Sgt. Cruz gets Bosco and Faith assigned to the Anti-Crime Unit for a few days so that they can track the guy down. At the scene of another supermarket fire the next night, Faith takes down license plate numbers, Cruz photographs the crowd and cars at the scene, and Bosco nabs the man he saw in the crowd the night before. The man turns out to be a fire buff, but Faith and Cruz's work bears fruit and they find their arsonist -- the son of Doug Maple, an NYFD arson investigator. A depressed Sully is still on leave, drinking too much, and sleeping on the couch at Ty's and Carlos' apartment; Doc connects with an attractive

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.