A silent alarm leads Andy and Swarek to the discovery of an illegal warehouse party, and to an injured John Doe — a homeless squatter who has been the victim of a brutal stabbing. While 15 Division works to contain the unruly teenagers to the scene for questioning, Andy and Swarek apprehend a surprising witness — Oliver’s 15-year-old daughter, Izzy. When Chris and Nick discover John Doe’s identity, things take a turn for the worse: he names Izzy as a material witness in his stabbing. But when the officers of 15 Division discover Izzy has disappeared, they move into emergency mode, tracking her down and keeping fellow officer, Oliver Shaw, from blurring the lines between being a protective parent and a lawful officer.