Sins (2)

Sins (2) splits its hour between a field and a fugitive, and keeps both running at full tilt.

In the field: Terry Ryan's body was found buried there last week, and now more corpses turn up in the same ground. Grace Foley looks at the pattern and reaches an uncomfortable conclusion. This is a ritual burial site, which reframes the whole case from one dead man with enemies to something older and stranger. Sue Johnston plays these moments beautifully; she has always been the show's quiet centre, and her Grace reading a field for what people did to each other on it is the episode's best recurring image.

In the meantime there is a live one to catch. Michael Kelleher, a convicted serial killer with sociopathic tastes who happens to be dying of cancer, has escaped from prison and taken prison psychiatrist Dr Hooper with him, reasons unclear. Boyd and the team race to find Hooper before whatever Kelleher has planned comes to pass. David Schofield makes Kelleher genuinely unnerving rather than merely shouty, which helps no end, and Michael Maloney gives the hostage a frightened dignity that raises the stakes.

And then there is Eve's thread, back in the lab, where Tara Fitzgerald's Dr Lockhart makes a discovery that lands like a trapdoor opening. It ties the burial site and the escape together more tightly than anyone would like.

Declan Croghan and Barbara Machin wrote it, Daniel Percival directed. The regulars are all present: Trevor Eve as DSI Boyd, Wil Johnson as DI Spencer Jordan, Félicité Du Jeu as DC Stella Goodman. Guests include George Rainsford as Luke Boyd, Ruth Gemmell as Linda Cummings and Alexandra Moen as Cathy Reading.

The two-parter closes well because it lets its three kinds of suspense feed each other: graves, hostage, lab result, each raising the temperature of the others. A dying killer with nothing left to lose is an old device but a dependable one, and here it earns its keep. Grim, controlled, and satisfyingly nasty about human nature.