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.

Tyler botches a takedown of a gang of rapists that nearly costs Nick his life, and leaves Ben to question Tyler's fitness on the job. Nick brings Harvey to Houle’s BBQ, which goes crudely awry.

Nick butts heads with J.M when they are assigned patrol together. Beatrice embarks on a new romance.

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.

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.

In the aftermath of the school shooting, the squad copes with the trauma as it affects them in ways they never expected.

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

The squad becomes involved in a feud with firemen; little mistakes cause consequences.