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.

As the other rookies hunt down a dangerous escaped convict, Swarek drags Andy through his undercover haunts on a mission he won’t explain. At first, Andy assumes Swarek is a rogue cop trying to settle scores from his undercover days. Then she realizes two things: he’s actually trying to track down a missing informant whose life is in danger now that his cover has been blown; and, that there is an undeniable attraction between them.

While working on a high-stakes gun raid, Andy and Gail stumble upon a victim of domestic abuse whose brutal experience in the system has taught her not to trust the police. When Andy promises to protect the woman from her abuser, she soon learns that it takes more than just following protocol to be good at her job. Meanwhile, the other rookies get caught up in the annual police retirement boxing match – a fundraising event known as “Fite Nite.”

Andy’s undercover skills are tested – and found to be lacking – during a citywide campaign to clean up the streets, when she’s tapped to pose as a prostitute in order to arrest unsuspecting johns. But the real test comes when Andy and Dov inadvertently put a vulnerable street informant’s life in danger, and it’s up to the two rookies to infiltrate a dangerous gun deal in order to save the trapped woman from a group of ruthless criminals.

A home invasion at an upscale address leads to a massive first response call that brings out the training officers in full force. After the scene is cleared, Andy and Traci remain behind with the terrified homeowner. When Traci is called away to deal with an emergency with her son, Andy is left alone to face the armed thief who is still prowling around the house.

Andy’s romance with Det. Luke Callaghan gets complicated when he chooses her for a special assignment - serving a search warrant for a bullet lodged in the head of a witness to murder. When the witness escapes, Andy risks her life to apprehend him, but later finds herself at odds with Luke over the next steps in the case. Meanwhile, the other rookies discover the shocking truth behind evidence from a fatal traffic accident.

A severe heat wave wreaks havoc on the city, forcing the rookies to work around the clock to keep the peace. In the midst of the chaos, Andy discovers that a serial rapist may have resurfaced to prey on vulnerable teenage girls. And when the extreme temperature precipitates a citywide blackout, Andy finds she’s cut off from all backup and must take.

After their High School Outreach assignment goes awry, Andy and Chris stumble on the victim of a vicious beating behind a nightclub. When the trail of clues leads them to discover the man’s assailant was a cop, the rookies are faced with a gut-wrenching moral decision – a choice that could dramatically jeopardize their future on the force. Meanwhile, the senior officers compete in a retraining exercise led by Frank Best, the new acting Staff Sergeant.

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’s attempt to avoid Swarek is thwarted when both are assigned to a prisoner transport. When things go awry and the inmate breaks loose, the two officers are led on a cat-and-mouse foot chase through the meandering woods. Meanwhile, Chris and Traci help Jerry reconstruct the missing notes of a vital court case, and Dov and Gail piece together the mystery behind an amnesiac John Doe.

What was to be a routine day for Andy is abruptly put on hold when her ex-copper father, Tommy, confesses that he might have committed a serious crime during one of his alcohol-induced blackouts while settling a score that has tortured him for years. As she and Swarek try to piece together what happened, little by little she begins to uncover the truth about the case that sent her father over the edge – evidence that could possibly send him to prison.

There’s a nervous tension in the air on Judgment Day for all the rookies at 15 Division who will have to undergo make-or-break assessments by Staff Sergeant Frank. But after the death of an unidentified girl at a house party – an emotionally harrowing experience that pushes all of her buttons – Andy begins to question whether she has what it takes to be a copper and contemplates handing in her badge.

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.

Andy and Gail go undercover as cocktail waitresses to clean up a drug-infested club, but get more than they bargained for when their fellow waitress turns out to be involved with a vicious criminal. Meanwhile, Traci wrestles with feelings for her old flame, Detective Barber, Dov tries to weather the storm when a young woman files a complaint against him, and Andy unwittingly opens up to Sam about her commitment to Luke.

Strange happenings and a full moon rattle the rookies. Andy and Sam investigate the theft of some severed heads from a medical lab. A particular man catches their attention as a suspect with his obsessive behavior. While trying to protect a young woman who could be the next target, Andy puts her life and Luke's in jeopardy.

The torching of a Laundromat is the latest in a series of arsons which the 15th Division must work. The list of suspects is long so Chris and Gail take to the streets while Traci interrogates a person found at the scene. Andy is left to deal with the widow who insists on entering the burnt-out building which ends with the two of them trapped inside.

A local car dealership is the backdrop for a Division 15 sting operation to crack down on suspects with outstanding warrants. However, when one of the captured criminals tries to bargain for a lighter sentence by offering insider information to Dov and Chris, it puts them in peril in a booby-trapped meth house. Meanwhile, Jo convinces Luke to help her on a high-stakes surveillance job. Trapped together in a hotel room, the two detectives finally have it out over their past, raising the question of whether they are really finished

Indications are that the East Jameson gang was involved in the murder of a police informant, so solving the case will be difficult. The pressure is on when Superintendent Elaine Peck sets up at the station. Elsewhere, Andy is paired with Detective Rosati who unintentionally makes Andy privy to a secret that involves Luke. Stressed out with her mother at the station, Gail is tasked with protecting an eight-year-old boy who's the only witness to the crime.

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.

Gail and Traci apprehend a man who mysteriously collapses at the station which in turn places Division 15 under quarantine. Andy and Swarek are after a brutal bank robber and his partner but it will take some out-of-the-box thinking to solve this crime. Dov goes out on a first date with the bomb tech who saved his life.

It's a race against the clock as Dov and Gail work under Swarek's expert tutelage in a stakeout operation to stop an Asian gang from killing a snitch. Meanwhile, at Mounted Unit training day, Andy and Chris join the rookies from Division 27 in a competitive equine training event that gets Andy back in the saddle - both personally and professionally.

While working a kidnapping case, Andy and Swarek find themselves on the scene of a car accident. As Swarek and the rest of Division 15 pursue the kidnapper and missing child, Andy remains at the scene with a woman trapped in her car. A transgression involving Gail puts Chris at odds with Dov. Andy concludes that it's time to re-evaluate her life.

When Traci and Andy are sent out on an undercover training exercise, they stumble upon a young woman who is about to die of an overdose. Meanwhile, Dov finds himself on a “ride-along” with a drug dealer and old friend of his deceased brother. Back at the station, Chris and Gail deal with a teenage boy they found tied up at a graveyard; sifting through the wreckage of their relationship, to try to get to the bottom of a bullying situation.

When Gail’s uniform is stolen from her car, she and the other rookies from Division 15 attempt to catch a cop-impersonating vigilante. A drug deal gone awry may offer clues to help Chris and Dov unravel the motive behind the cop masquerade. Meanwhile, Andy and Sam’s inability to stay away from each other poses a life-threatening risk to Swarek.

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.

While tracking down a police car stolen by students as a prank, Andy and Swarek pick up the trail of a teen who robbed and assaulted a local criminal.

When Dov walks into a robbery in progress and shoots a black teen, the community calls for him to be investigated.

Traci worries that she mishandled the investigation into a car accident that yielded a dead body; Chris realizes he has feelings for Gail.

Andy answers a domestic disturbance call to find the social worker on the scene is her estranged mother; Sam, Nick, Chris and Gail search for a mother and her two children; a stash of guns recovered by Detective Barber turns up on the streets.

Oliver Shaw's teenage daughter, Izzy, witnesses the brutal stabbing of a homeless squatter; when Izzy goes missing, officers rush to track her down.

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

When a pattern emerges among several cases of missing women, Gail goes under cover to investigate; Dov and Chris discover a body, leading them to believe Gail is in danger.

When Dov and Chris discover a missing girl's body in a ravine, Detective Luke Callaghan returns to oversee the investigation; when the officers learn that Gail has been abducted, they rally to track down her captor.

The officers try to prevent dangerous fallout when a laptop containing sensitive information is stolen; a wedge is driven between Sam and Andy.

Andy and Nick investigate when a neighborhood drug lord threatens a priest's life; a young drug-runner's refusal to turn informant leads Traci to make a decision about her career; Chris and Swarek butt heads; Dov's relationship takes a dark turn.

A chaotic night at the station leads to an investigation by Internal Affairs; Gail struggles to recover from her harrowing abduction; Andy discovers a secret about Nick's past.

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.

On her first day back, Andy is forced to work a bank robbery case with newly promoted Swarek; a distraught woman gives Nick perspective on his life with Gail; a bombshell is dropped on Noelle.

Andy and Officer Cruz butt heads when a disturbed woman forces them to make a crucial decision; an armed burglar is sought after a string of ATM robberies; Dov and Chloe have to work together.

During a routine traffic stop, Gail and Andy find a teenage boy bound and gagged in the trunk of a car; Oliver, Chris and Swarek track a gunman.

When an arrest reveals that drugs contaminated with a deadly bacteria have hit the street, the squad rushes to control the situation; Marlo reveals a shocking secret; Dov suspects Chloe of hiding secrets.

When the investigation of a missing girl is linked to a past case, Detective Luke Callaghan comes back to help with search; Traci realizes she needs to get past Jerry's death; Sam and Andy face their past.

When a missing persons case is reopened, Swarek teams with his training officer to solve it; Chloe and Dov deal with a witch and her client.

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.

The squad searches for Chris' son Christian after he is kidnapped.

A routine drug bust turns into Traci's first murder case; Swarek, Oliver, Chris and Dov spend a weekend at Oliver's cabin; Andy and Sam both have confessions to make.

Andy finds out Marlo has been carrying out an unauthorized investigation into a pedophile; the drug sweep Traci is overseeing takes an unexpected turn when Sam leaves to help Marlo.

When Andy and Chloe respond to a routine 911 call, they are blindsided by an unseen shooter out for revenge.

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.

It's a day of firsts as Oliver gets promoted to Acting Staff Sergeant and Andy is tasked with training 15 Division's newest rookie, Duncan Moore. But when Andy and Duncan respond to a messy homicide at a pawnshop, it's clear this rookie is going to give Andy the challenge of a lifetime.

With Fite Nite looming, Inspector Jarvis sends the officers of 15 Division to seize all "proceeds of crime" – anything purchased with money earned illegally. But when Andy and Nick's seizure at an illegal gambling house leads to a suspicious confession, Andy recruits Sam to help figure out who's lying, why, and where the money is, before anyone gets hurt.

When a tenement-building shooting leads to the discovery of an executed gang leader, 15 Division must race to find the killer before a gang war breaks out. As the murderer zeroes in on the one witness who can tie him to the crime, Andy and her rookie, Duncan, are put to a life-and-death test of true police heroism.

When 15 Division goes undercover at a club-land bar that's a possible hub for illegal handguns, Chris's erratic behaviour and concern for a specific drug dealer make Dov suspicious. Meanwhile – after learning Duncan has made serious professional allegations against her – Andy decides to help Sam with a missing person's case that takes a dark turn.

As the officers of 15 Division try to hunt down the killer of Brian Gowdy, Andy and Sam go on the road to interview a list of inmates at Millburn Penitentiary. All are known associates of the prime suspect; one person on that list happens to be none other than Jay Swarek, Sam's elusive father.

Oliver prepares Andy to defend herself at Duncan's dismissal hearing.

Dov suspects Chris isn't ready to get back on the right track; Steve tells Traci he's about to raid a gambling den frequented by her husband.

When the Division helps tenants move out of a condemned subsidized-housing complex, they discover a badly beaten man in one of the empty units.

A bomb explodes in a parking garage. The 15 Division must stop the suspect.

The officers of 15 Division work to track down Ted McDonald. But even after catching him, they realize Ted has more targets set to explode out there. The clock is ticking…

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

Andy contemplates her future with Sam after learning heartbreaking news. Andy meets a teen in need of protection.

A riot breaks out at a women’s correctional institute while Andy, Juliet, Nick, and Gail are there to transfer prisoners. They end up separated and in a lock-down situation that finds Andy and Juliet trapped with a woman desperate to prove her innocence.

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.

Andy and Sam are shocked to learn that Oliver is the prime suspect in IA’s corruption investigation into 15 Division. What’s worse, they only have until end of day today to find Chris Klem – the missing explosives-dealer – and clear Oliver’s name before he takes the fall.

A community-outreach baseball game is interrupted by a drive-by shooting. Sam plans a getaway with Andy.

Andy and Sam are shocked to learn that Oliver is the prime suspect in IA’s corruption investigation into 15 Division. What’s worse, they only have until end of day today to find Chris Klem – the missing explosives-dealer – and clear Oliver’s name before he takes the fall.

Andy, Dov, Gail and Nick undertake a risky plan; Traci shadows Steve Peck, hoping to calm her fears about his involvement in the bombing.

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.

Dov and Andy cover a music festival where a girl ends up dead due to drugs. Gail goes to court and is unsure whether lying for her brother is the right thing to do. Nick gives Juliet another chance.

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?