David Hare concludes his trilogy of films about MI5 renegade Johnny Worricker with another fugue on power, secrets and the British establishment. Johnny Worricker goes on the run with Margot Tyrell across Europe, and with the net closing in, the former MI5 man knows his only chance of resolving his problems is to return home and confront prime minister Alec Beasley.

A rogue submarine captain pulls together a misfit crew to go after a sunken treasure rumored to be lost in the depths of the Black Sea. As greed and desperation take control on-board their claustrophobic vessel, the increasing uncertainty of the mission causes the men to turn on each other to fight for their own survival.