Nolan is given some life-changing news and invites Grace over for a homecooked meal in his newly remodeled kitchen. Meanwhile, each unit is tasked with following up on dormant cases in the hopes they can uncover new leads.

When a new designer drug hits LA streets, it turns users into “zombies,” and Officer Nolan and the team have a Halloween they won’t soon forget. Back at home, Lucy questions whether her apartment building might be haunted.

Officer John Nolan is forced to spend a week in solitary confinement in a quiet border town with a young local officer who is in need of some training. Meanwhile, Sergeant Bradford and Officer Chen discover that looks are deceiving and go undercover together in a possible drug trafficking case.

The team comes together to celebrate John and Bailey’s wedding; meanwhile, Celina discovers a discrepancy in her case, leading to a new discovery. Elsewhere, Lucy and Tim’s relationship is put to the test.