Guilt ridden Officer Nick Barron returns to work following a deadly shooting; Ben Chartier's transfer to Station 19 from Québec's rural police force turns rocky after a split-second decision triggers an internal investigation.

A showdown between rival street gangs goes terribly wrong, leaving Ben’s life in danger. Squad 19 gathers at Marie’s for the Sergeant’s party and Isabelle discovers Nick may have feelings for someone else.

The first of the month brings “Welfare Day” to 19 – Nick and Ben handle an array of belligerent civilians; the day caps off with a cataclysmic domestic disturbance.

Squad 19 is pulled into a big raid. Nick and Ben clash over a politically explosive DUI while Isabelle and Nick find common ground when Theo starts to act out.

An amber alert ripples through 19. After realizing he’s been shutting Audrey out, Nick makes a strong commitment to her. Ben continues to date Amelie without telling Nick, adding another stress to their partnership.

The squad is devastated when one of their own is brutally assaulted and left clinging to life, causing personal vendettas to collide with protocol in the aftermath.

In the climactic season finale, Nick receives devastating news, and struggles to contain his explosive response. A surprise visitor lands in Ben's life, forcing him to make some very hard decisions.

After the arrest of a misunderstood homeless man and the retrieval of a runaway, Nick and Ben realize that not everyone can be saved.

Amelie takes a chance on Ben, while Nick and Isabelle receive shocking news about Theo.

The identity of the mole is revealed.

With the mole on the run, a devastated squad turn on each other, and on themselves.