Episode 6

The season ends with Luther on the run, suspected of murder and unable to clear his name through the normal channels. The people who should be backing him are the ones who have to treat him as a suspect, and the department he has spent his career inside has become the place he cannot go.

And his ally in all of it is Alice Morgan. That alone tells you how far the show has travelled. The woman he could not convict in the first episode is now the only person he trusts, and the two of them set out together to settle the score with the real killer. It is a pairing that should not work and does, mostly because Ruth Wilson and Idris Elba play it with no sentiment at all. They are two people who understand each other's capacity for damage.

Neil Cross wrote the finale and Stefan Schwartz directed it, and the whole supporting cast turns up to hold the line: Steven Mackintosh's Ian Reed, Saskia Reeves's Rose Teller, Paul McGann's Mark North, Warren Brown's Justin Ripley, Dermot Crowley's Martin Schenk and Matthew Marsh's Russell Cornish, with Indira Varma's Zoe at the centre of the wreckage Luther leaves behind.

The revenge mission takes the episode outside the usual procedural shape. There are no interview rooms here, no paperwork, just two people moving through a city that has turned against one of them. The chase is the plot, but the argument underneath it is about guilt and who gets to decide it. Luther has spent the season proving that the law is not the same thing as justice, and the finale asks him to act on that belief.

It ends where it has to, with the real killer dealt with and Luther's name still in the mud. The season closes on a man who has won nothing and lost almost everything, which is exactly the note the show had been building toward.