Gibson comes face to face with the depths of Sally-Ann's desperation, while Burns has to confront his guilt at pursuing Sally-Ann as a conspirator rather than a witness. Gibson and Dr Larson clash over their different view of Spector - patient or prisoner? Meanwhile, Anderson and Ferrington are dispatched to London to discover if Spector can be linked to an old murder there.

The series concludes as Gibson and Anderson put fresh evidence to Spector, with explosive results. Spector's new-found friendship with another inmate develops, with devastating consequences.