Pieta (2)

Part two turns the case outward. Boyd vows to track down the ring of war criminals behind the Bosnian grave, and the hunt reveals they have not scattered across the world at all. They live in Britain and work in Britain, and the trail that should have been historical has a live edge. The deaths are a decade old, but the investigation keeps colliding with a drug deal taking place in the present, and the two lines of inquiry refuse to stay separate.

That collision is the point. The episode threads the old atrocity through a contemporary crime, so the squad is chasing current criminals and the ghosts of a war at the same time, with each case explaining the other. It is ambitious plotting, and it mostly works, because the show never lets the history become decoration. The victims of a decade ago stay central, and they are the reason anyone is investigating at all.

Declan Croghan and Barbara Machin wrote it, with Philippa Langdale directing. Trevor Eve leads as DSI Peter Boyd, with Sue Johnston as Dr Grace Foley, Tara Fitzgerald as Dr Eve Lockhart, Wil Johnson as DI Spencer Jordan and Félicité Du Jeu as DC Stella Goodman. Sean Harris plays Radovan Sredinic, Jacek Koman Jovan Petropecic, Anna Madeley Anna Vaspovic, Emil Hostina Josif Gorvodic and Anatole Taubman Stevan Steznovic.

Pieta closes series seven, and it sends the show out on a strong note. The war criminal plot gives Sean Harris and the guest cast room to do their worst, and Boyd gets the kind of case he was built for: one he can be properly angry about. The series has always known that Boyd is at his best when he is chasing evil that has settled into comfortable routines.

As finales go it is a sombre one, and that feels right for the season. Nobody gets a celebratory wrap-up. What they get is a promise kept and a great deal of damage left behind. The show trusts the audience to sit with that, and it earns the trust.