Andy McNally’s first shift on the job turns into mayhem when shots are fired in a downtown rooming house. In the midst of the chaos, Andy triumphantly makes her first big arrest – a suspected drug dealer – who turns out to be Sam Swarek, an undercover officer from her own division. She makes up for her grave mistake by going face to face with a dangerous gunman who already has one man’s blood on his hands.

After a routine speed trap leads to a messy accident on a city highway, Chris and Gail find one of the cars mysteriously empty and quickly realize that its license plate matches the one being broadcast in a citywide “Amber Alert” – a nine-year old girl has been abducted and the driver of the vehicle is the prime suspect. A whirlwind manhunt ensues involving a complex interrogation of the missing child’s parents. As always, everyone has a secret.

Andy and Chris accidentally screw up one of the biggest drug busts of the decade when they arrest one of the players. In an effort to save the operation, Swarek and Andy go undercover to make the drug buy. When Andy realizes that their bait and switch has created an ambush that will endanger Swarek’s life, it’s all hands on deck as the coppers of 15 Division rush to save the life of one of their own.

Andy's world explodes by a seemingly senseless act of violence during a concert shooting. When she sets out to unravel the details, she comes into direct conflict with Luke's former partner, Detective Jo Rosati, a new detective with Division 15. As Rosati investigates the case, sparks soon fly between her and Luke.

Detectives Callahan and Rosati are at odds over how to correlate and interpret the facts of two vicious crimes. Luke feels strongly that the latest woman attacked on her watch is connected to an unsolved rookie's murder, but his erratic behavior gets him kicked off the case. Andy may be in serious trouble when Luke urges her to follow through with his hunch on the crimes.

Blaming herself for Swarek’s mysterious disappearance and fearing for his life, Andy struggles to find a lead in the case. Will Andy and the other rookies find him in time? Little do they know that shocking events triggered by this investigation will incriminate one of their own and may also put an end to Andy’s career.

After a three-month suspension, Andy faces an official tribunal that will decide if she should be reinstated; a drunken driver (William Shatner) with a grudge against the police causes a multicar crash.

After losing a key witness in an upcoming trial, officers from 15 Division must turn to a man who claims to be psychic.

A violent pedophile escapes during an emergency hospital visit and abducts a girl; Andy faces a serious decision; Chris considers a transfer.

Nick and Andy go missing while working under cover to infiltrate a meth pipeline; Swarek and the other officers find themselves in the middle of a rescue operation; Andy works to deal with all the change going on around her.

A robbery on a casino-bound bus filled with seniors threatens Frank and Noelle's wedding; Traci loses Noelle; Andy and Nick share an intimate moment.

Following violent, targeted attacks on 15 Division, the officers must piece together a past crime in order to find Oliver; the shooter's plan is revealed.

In the aftermath of the night's traumatic events, Andy and Dov try to pull themselves together at an all-night diner, but are caught off-duty and off-guard in a volatile diner hold-up. Meanwhile, the weary officers at 15 Division struggle to contain the evening's collateral damage under the watchful eye of a tough new Inspector.

Andy and Sam return to work; Andy is attacked at Traci's place and Sex Crimes Unit tries to take over the case

Nick receives new information on his tragic past, and goes off the grid to track someone down; Nick is forced to tell Juliet about his secrets.

As the officers of 15 Division try to move on from the corruption scandal, a heat wave hits and Jarvis opens the division to the public as a cooling station. Andy heads out with a very-pregnant Marlo to find a volatile woman who’s gone missing after group therapy, but neither Andy nor Marlo are prepared when Marlo suddenly goes into labor.

With the 15 Division restructuring looming, Andy and Sam’s wedding comes just in time for the gang to celebrate one last hurrah. But when Andy is taken off-course by a hitchhiker and then stranded on the side of a dead-end road with a dying man, she finds herself with no way to get help – or let Sam know she hasn’t bailed. Will she save the man’s life? Will she make it to her wedding?