Episode 4

The season's bill comes due here. Luther is reeling from the death of his friend, and the grief has hollowed him out at exactly the moment Cornelius's terrible retribution is closing in on everyone connected to him. And the killer is loose in London, determined to finish a final macabre masterpiece. The man who usually hunts such people can barely hold himself together.

So Halliday takes the lead. It is the right call and the show is brave to make it, because watching Luther be absent from his own case is more uncomfortable than watching him dominate it. He keeps drifting back to the edges, compromised and half-present, while the investigation carries on around him, and the episode earns its tension from that gap. Wunmi Mosaku steps up properly, running the hunt with the quiet authority the role needs. The change suits the hour, and Mosaku earns it. Her leadership is not just a plot move. It is the show admitting that Luther's method has limits.

Neil Cross wrote it, Jamie Payne directed. The cast is deep and knowing: Dermot Crowley's Schenk, Enzo Cilenti's Jeremy Lake, Gary Hailes's Donnie McKinney, Sonita Henry's Daria Shubik and Anthony Howell's Palmer all pull weight, while Nicholas Asbury's DCI Woodgate and Robert Bannon's Andy King give the station a bureaucratic edge that suits a finale. Paul McGann's Mark North reminds us how wide the blast radius has become. Patrick Malahide's George Cornelius watches it all with the quiet satisfaction of a man whose plan is working.

The masterpiece the killer wants to finish is the episode's cold centre. Everyone else is racing toward it, and Luther least of all can afford to arrive late.

It ends with the retribution landing and Luther still in pieces. The season finale has left him nowhere left to hide.