Pieta (1)

A road accident in Britain does something no traffic incident should do: it throws up a DNA link to a murder in the Bosnia conflict, and the Cold Case squad is suddenly working a case older than the unit itself. The link lands hardest on Eve, who dealt with mass war graves before and knows what she is walking back into. The bodies of a mother and son come out of a mass grave in Bosnia. The mother looks local. The boy was not Bosnian, and that one contradiction is the whole case.

The title comes from the Pietà, the image of a mother holding her dead son, and the episode carries that image without ever spelling it out. But the show knows the value of a small contradiction: a boy in a grave who should not be there. The team has to piece together who these two people were from the DNA and the records, from the memories of people who lived through the worst of it, and none of it answers the obvious question of why the boy was there at all.

Declan Croghan and Barbara Machin wrote it, and Philippa Langdale directed. Trevor Eve leads as DSI Peter Boyd, with Sue Johnston as Dr Grace Foley and 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.

The episode is careful with its history. The war stays in the background, but the writing keeps its focus on the people the conflict swallowed, on the DNA and the paperwork that are all that is left to reconstruct them. It is grim material, handled without melodrama, and Eve carries the weight of it visibly. This is her case as much as Boyd's.

Pieta (1) is one of the show's more serious outings, and it earns its seriousness. There is no clever killer waiting to be unmasked, just the aftermath of a war trying to pass itself off as a case file. The identity of the boy is the thread left dangling, and it is a good one. The answer arrives next week, but the picture it will paint is already bleak enough.