Episode 1

The episode opens with a return to work. DCI John Luther comes back after a traumatic arrest and lands straight on a double murder: the parents of a former child genius, killed in their own home. Luther takes one look and names the daughter as the killer. But getting there was the easy part. Proving it is another matter, and the whole engine of the hour is the gap between what he knows and what he can take to court.

The daughter is Alice Morgan, and she is not the sort of suspect who sits still. With no evidence against her, Luther is left in a battle of wits, and Alice enjoys the fight rather more than he does. She has set her sights on him and on his estranged wife Zoe, so the professional case quietly becomes a personal one. It is an uncomfortable arrangement, a detective and a killer who understand each other far too well.

Around the margins, the usual machinery turns. DCI Ian Reed and DSU Rose Teller supervise, DS Justin Ripley fetches and carries, and Mark North (Paul McGann) hovers in the background of Luther's wrecked marriage. Anton Valensi's Henry Madsen keeps the police side of things busy while the real fight happens elsewhere.

Neil Cross wrote it and Brian Kirk directed. Idris Elba carries the episode with the coiled intensity he would bring to the whole series, and Ruth Wilson's Alice is the most dangerous person in the room from her first scene. Matthew Marsh, Saskia Reeves, Warren Brown, Indira Varma and Glen Stanway round out the cast.

The deduction is the hook, but the failure is the point. Luther solves the crime and still loses, because knowing something and proving it are different trades. Alice walks away, and the episode ends with the two of them circling each other like people who have just agreed to a long war.