A service officer in the Marine Fisheries department works with the local police to solve crimes on Cape Cod.

After discovering a lead on Sherry's murder, Jackie becomes determined to solve the case. Junior finds himself trapped, and Ray connects with his CI in ways that are unprofessional.

Jackie returns to rehab, but only to help further her investigation. Ray starts closing in on Osito at the same time he and Renee cross the line. Junior takes the first step to becoming a soldier.

Jackie finds out where Krista Collins is staying, but gets pulled back into her own life. Ray comes face to face with Osito, Junior tries to reconcile with Donna's family.

Jackie goes on a bender, threatening everything she's got going for her, throwing her sobriety out the window, and ultimately putting Krista Collins in danger like never before. Junior has to prove himself in a new way. Ray and Renee go on a date.

Jackie and Junior struggle to cope in the wake of a traumatic event. Ray's investigation picks up speed. Ray is there for Renee when she really needs him.

When Jackie realizes Junior's involved with Sherry Hunter's murder, she enlists Ray and the entire CCINU to track him down -- before Frankie has him murdered. Renee finds herself deeply questioning her budding relationship with Ray.

Jackie and Ray try to return to business as usual after a depressing failure, only to learn the case might not actually be closed.