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.

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.

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.

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 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 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.