Yahrzeit (2)

Yahrzeit (2) picks up the Dusniak case and immediately knocks a hole in it. The team starts looking properly into the family background and finds the DNA does not match. For a show built on forensic certainty, that is a nasty little earthquake: the science, usually the one thing Boyd can lean on, is telling him the family story is wrong.

And then Ben goes missing, which turns an investigation into a crisis. Boyd tries to force the truth out of David, who is confused and frightened and not much use to anyone, least of all himself. It is the sort of pressure-cooker scene work this show does well, with Trevor Eve leaning across a table and patience visibly running out. Meanwhile Stella takes her own thread and runs it all the way to Poland, hunting down what actually happened there during the war rather than what the family has spent decades saying happened. Félicité Du Jeu gets some proper material out of it, and the episode is better for letting her carry a storyline alone.

There is a personal line running under all of it too: Boyd grows closer to Sarah as the case tightens around him, which gives the man something to be human about between interrogations. Whether this softening suits him is a matter of taste. He has always been more interesting slightly bruised.

Declan Croghan and Barbara Machin wrote it, Tim Fywell directed. Alongside Eve, Sue Johnston returns as Dr Grace Foley, Tara Fitzgerald as Dr Eve Lockhart and Wil Johnson as DI Spencer Jordan. The Dusniaks are played by Sophie Tait (Bernadetta), Andrew Armour (Marek), Ania Sowinski (Adriane) and Richard Klvac as Marek in his younger days, with Saskia Schuck as Hanna Muller.

Second parts live or die on whether the payoff earns the setup, and this one largely does. The 1945 murder, the daggers, the survivor testimonies and the mismatched DNA all click together by the end, though the clicking hurts people who have done nothing worse than survive. That was true of the history too.

A solid close to series six's strongest story. The show trusts you to sit with uncomfortable answers, and mostly it is right to.