On her last day of work, homicide detective Sarah Linden is drawn into a new case; City Councilman Darren Richmond prepares for an important forum with the mayor.
Rosie's teacher provides a new piece of evidence; Richmond's team plans an anti-crime TV commercial; Stan asks his colleague for help to find Rosie's killer.
The police connect Rosie to a suspicious website; the waterfront project stalls; Stan faces his demons; Mitch learns secrets she never knew about Rosie.