The Promise (1)

Kate and Duncan are inside a prison running an enquiry into bullying when Pace Tierney, an old adversary of Red's, takes the place over. Tierney is the man who once held Red hostage and nearly broke him, and he runs the riot the way he runs everything: loud, cruel and in charge. Kate and Duncan end up among the hostages, though Duncan accepts the chance to leave with a lack of chivalry the script doesn't bother to excuse.

The violence is not abstract. Tierney burns a warder alive and pours turpentine over Kate before Red brings in the riot police. The injured are moved to a nearby hospital, where a sympathetic young doctor, Philip Ryder, does what he can under an abrasive surgeon called Mr Henderson. And then, in the middle of the recovery, the killing starts. Tierney is murdered. So are Leo Symons and Gerry White, the two prisoners who had reported the bullying. Whoever is doing this knows medicine, or at least knows enough to move around a hospital without being noticed. It's a place full of locked doors and quiet corners, the worst possible setting for a hunt.

At home, meanwhile, Susan has found out about Red's affair with his therapist, Jaine Ellis. It's a smaller wound than the ones being opened in the hospital, but the show treats it as serious. Everything in Red's life is bleeding at once, and he has to police a riot while holding himself together.

Boris Starling and Lizzie Mickery wrote it, David Drury directed. Liam Cunningham's Tierney is a proper menace, with Neil Dudgeon's Warren, Tom Ellis as Ryder, and Phil Atkinson, Michael Bertenshaw, Leo Bill, Jimmy Flint, Paul Copley, Darrell D'Silva and Olivia Busby around him.

The episode ends with the killer loose among the injured and nobody sure who to trust. Red has been here before with Tierney, and that history makes none of this easier.