A month after the evidence room bombing, Andy and Sam return from a much-needed vacation ready to work. But when Andy is attacked by an intruder at Traci's place and the Sex Crimes Unit steps in to take over the case their way, 15 Division will have to decide whether to take matters into their own hands.

Andy debates her future with Sam after learning the heart-breaking news that Marlo is pregnant with his baby. But Andy's ideas about what makes a perfect family are put into perspective when she meets an out-of-control teen who needs to be protected from her own conservative family.

A riot breaks out at a women's correctional institute while Andy, Juliet, Nick, and Gail are there to transfer prisoners. They end up separated and in a lock-down situation that finds Andy and Juliet trapped with a woman desperate to prove her innocence.

When Nick's estranged older brother emerges with new information on someone from their tragic past, Nick goes off the grid to track the man down. But Juliet is hot on his heels, and Nick is forced to let her into the secrets of his past.

When Traci is a no-show for her first raid, 15 Division fears the notoriousballoon dealer they're after has kidnapped her. But when Andy realizes that the serial rapist who was never caught is back, it's all hands on deck to find Traci - while Traci faces off with her captor and tries to escape before it's too late.

After a community-outreach baseball game erupts in a drive-by shooting, Gail's relationship with her brother, Steve Peck, is put to the test in the search for the shooter. Meanwhile, Sam plans a getaway with Andy up to Oliver's cabin, which goes off the rails in every possible way - except one.

Andy and Sam are shocked to learn that Oliver is the prime suspect in IA's corruption investigation into 15 Division. What's worse, they only have until end of day today to find Chris Klem - the missing explosives-dealer - and clear Oliver's name before he takes the fall.

With Oliver still the prime suspect in the bombing of 15's evidence room, Andy, Dov, Gail, and Nick undertake a risky - and potentially career-ending - plan to prove that Commissioner Alonso Santana is corrupt. Meanwhile Traci shadows Steve Peck, hoping to calm her fears about his involvement in the bombing.

As the officers of 15 Division try to move on from the corruption scandal, a heat wave hits and Jarvis opens the division to the public as a cooling station. Andy heads out with a very-pregnant Marlo to find a volatile woman who's gone missing after group therapy, but neither Andy nor Marlo are prepared when Marlo suddenly goes into labor.

Now that Sam and Marlo's baby girl has arrived, it's clear nothing could have prepared Andy for this moment. So when Juliet offers Andy an opportunity to leave town for 4 months on an undercover project, Andy starts to consider it. Meanwhile, Jarvis reveals the shocking news that 15 Division will be restructured following the corruption scandal.

With the 15 Division restructuring looming, Andy and Sam's wedding comes just in time for the gang to celebrate one last hurrah. But when Andy is taken off-course by a hitchhiker and then stranded on the side of a dead-end road with a dying man, she finds herself with no way to get help - or let Sam know she hasn't bailed. Will she save the man's life? Will she make it to her wedding?