DI Tom Thorne is a London cop, a complex and headstrong character, scarred both inside and out by the cases from his past. Though his compulsion to make every case personal is resented by his colleagues - including medical examiner Phil Hendricks (Aidan Gillen) and former partner, Kevin Tughan (Eddie Marsan) - his dogged investigations leave them no choice but to follow where others fear to tread. Sleepyhead: Thorne is dragged back into the nightmares of his past, as he heads up the investigation into a series of horrifying attacks on young women by a killer as sadistic as he is terrifying. Scaredycat: Two sets of connected murders puts Thorne and his team, including a fiery but troubled new recruit, Sarah Chen (Sandra Oh), on the back foot. Could Thorne be up against a pair of brutal serial killers, working together?