When Dov and Chris discover a missing girl's body in a ravine, Detective Luke Callaghan returns to oversee the investigation; when the officers learn that Gail has been abducted, they rally to track down her captor.

The officers try to prevent dangerous fallout when a laptop containing sensitive information is stolen; a wedge is driven between Sam and Andy.

Andy and Nick investigate when a neighborhood drug lord threatens a priest's life; a young drug-runner's refusal to turn informant leads Traci to make a decision about her career; Chris and Swarek butt heads; Dov's relationship takes a dark turn.

A chaotic night at the station leads to an investigation by Internal Affairs; Gail struggles to recover from her harrowing abduction; Andy discovers a secret about Nick's past.

A violent pedophile escapes during an emergency hospital visit and abducts a girl; Andy faces a serious decision; Chris considers a transfer.

When the investigation of a missing girl is linked to a past case, Detective Luke Callaghan comes back to help with search; Traci realizes she needs to get past Jerry's death; Sam and Andy face their past.

Andy finds out Marlo has been carrying out an unauthorized investigation into a pedophile; the drug sweep Traci is overseeing takes an unexpected turn when Sam leaves to help Marlo.

When Andy and Chloe respond to a routine 911 call, they are blindsided by an unseen shooter out for revenge.

Following violent, targeted attacks on 15 Division, the officers must piece together a past crime in order to find Oliver; the shooter's plan is revealed.