When a suspected pedophile is found severely beaten, Andy discovers that Marlo has been carrying out an all-out, unauthorized investigation into the man. Andy and Swarek must scramble to cover for Marlo's unprofessional conduct before she is exposed. Meanwhile, Traci oversees a major drug sweep, assisted by Chloe, Nick, Dov and Gail, but when Sam leaves his post to help Marlo, the operation takes an unexpected turn.

In the wake of violent targeted attacks on 15 Division, Andy, Swarek and their fellow officers begin to piece together a past crime in order to find out what has happened to Oliver Shaw. While the squad is desperately trying to find Oliver, Dov and Wes face off about what's best for Chloe. And as the shooter's plan is finally revealed, it may be too late for some of the officers of 15.