DCI Carl Morck returns to work after a near-fatal incident and finds himself head of a new department. A prosecutor faces a tough day in court.

Carl and Akram recreate the fateful ferry journey on their way to the Isle of Mhòr. A frustrated Rose makes her case for joining their Department.

Rose goes to the island to find out what Carl couldn't. Akram finds a note which sends the investigation in an entirely new direction.

The police detain a suspect for the Leith Park shooting. Carl returns to the scene of the crime, before losing his temper in public once again.

The kidnappers give their victim a clue as they press her for an answer to their question. Dept. Q gets closer to unravelling its own riddle.