As Chloe and Sam lie in the hospital between life and death, Andy and Dov get stuck in a diner when an armed robbery takes place. Gail chops her hair off and Andy confesses to Nick that she still loves Sam.

Clumsy new rookie Duncan gives his training officer, Andy, a run for her money while trying to solve his first homicide. Swarek's sister warns Andy against Sam and Oliver replaces outed Sergeant Frank Best.

Serving a warrant to confiscate items from an illicit gambler, Dov and Wes come face to face. Gail dumps Holly. Chris plans fight night; Duncan withdraws and Nick Collins takes his place. Chloe assists him.

Andy McNally risks her life when her rookie Duncan has a panic attack and simply turns off his radio instead of backing her up. Gail comes face to face with an orphaned little girl whose mother was gunned down in a laundry room.

The rookies undercover mission is aborted when Chris Diaz comes face to face with his personal drug dealer whom he arrests, botching up the mission. Chloe alerts Dov that his friend Chris might be in trouble but just how deep is he in?

Nick and Gail and Sam and Andy pair up to solve the case of Brian Gowdy's murder. The plot thickens with both a cheating wife and Sam's jailed father being more or less involved in the murder.

Investigating a firebombing in Little Italy, the rookies find a thumb in a trash bag. Andy faces off with Duncan at his hearing; Chris ditches work and Dov goes after him, forgetting Chloe's birthday.

Following Dov's discovery of Chris's cocaine problem, Chris seems to have gotten on the right track. He's going to meetings, he's clean as a whistle - and he sure as hell doesn't need a babysitter. But while working a residential home invasion case, Dov discovers that Chris might not be ready to change after all. Back at the station, Steve lets Traci know that he is about to raid an illegal poker house where her ex, Dex, is a regular. With Traci's custody battle heating up, she knows Dex's arrest would end it once and for all; but does she really want Leo's father to ...

On moving day, the trial run for city's new body cam is deemed mandatory and when a an officer forgets to turn it off her slip-up is caught on camera. Chloe signs the divorce papers and Chris gets into rehab. Gail and Nick partner up and bring in two teenage siblings for possession of stolen property but Nick later finds out the reason they do and helps them out. Andy and Chloe walk in on an assault and the suspect escapes but when he shows up to the hospital to visit the victim, they find out they stumbled into a human trafficking ring.

Sam offers Andy a key to his apartment but she refuses. Duncan returns to active duty and requests to ride with Andy. Chloe and Andy are stopped while on patrol when a Parking attendant chases a car on foot after the driver didn't pay but moments later an I.E.D explodes in the parking structure which left one woman injured. A second bomb goes off in downtown, killing one and injuring 6, which makes the detectives think it's a mob hit aimed at eliminating Aiden Kelly, head of the Irish mob. When Duncan makes a rookie mistake he is handcuffed in a car wired with a bomb ...

Andy tries to be cool about the joint investigation with Intelligence which brings Marlo back into Sam's life, meanwhile Chris returns to active duty. After a bomb was found under the car of Judge Constance Sullivan's nanny, Andy and Oliver finds Ted Mcdonald and bring him in but soon after the team realizes the bombs aren't meant for the parents but for their children, for maximum suffering. After Sam gets the whereabouts of the last bomb he decides to take a look at the evidence in case Ted was right about the corruption in the police force but when he asks Andy to ...