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.

Cast: Jamie Dornan, Ruth Bradley, Aidan McArdle, Gillian Anderson, Colin Morgan, John Lynch, Stuart Graham, Krister Henriksson, Richard Coyle, Cathy White, Conor MacNeill, Aisling Franciosi, Denise Gough, Chris Patrick-Simpson, Bronagh Taggart