The most unvarnished, uncompromising and realistic police drama ever returns for another hard-hitting season. McNutty has been demoted to harbour patrol. Daniels is in the police-archive dungeon, Prez is chafing in the suburbs, and Greggs is stuck behind a desk. Meanwhile, on the docks of Baltimore harbour, the rank and file scrounge for work and the union bosses take illegitimate measures to reinvigorate business, but a horrific discovery is about to blow the whole port inside out. While the detail is on ice, a new case begins.