A group of young and ambitious rookie cops continue to navigate the emotional trials and tribulations of their professional and personal lives. After three years on the job, these rookies are well on their way to becoming experienced officers, but at what cost? It's been six months since Andy McNally and Nick Collins left for their undercover operation. But while they were gone, everything seems to have changed at 15 Division.

Andy and Officer Marlo Cruz, Swarek's new girlfriend, butt heads on their first patrol together. Their different ways of handling the job are put to the test when they confront an emotionally disturbed woman who is losing control - and explode when one of them is forced to make a crucial life-saving decision to pull the trigger. Meanwhile, the rest of 15 Division is hunting down an armed burglar with a novel MO after a string of ATM robberies, and Dov is forced to work with new rookie Chloe Price after their indiscreet first encounter.