Yahrzeit (1)

A parcel arrives for Boyd, no sender, and inside it a Nazi ceremonial dagger with a Cold Case reference number taped to it. That is how Yahrzeit (1) opens, and it is one of the better cold opens the show has managed. The number points to the unsolved murder of a young girl in May 1945, and there is an extra twist of the knife: Mel, presumably the late Mel Silver of the original squad, had been working this same case before she died. Nobody on the team quite knows what to do with that.

The second thread turns up in the bricks. A London flat is being renovated when workers pull a bloody Nazi dagger out of the fireplace, which is not the sort of thing you find behind the plaster every day. Two daggers, one dead girl, sixty years of silence: Boyd and company now have a case, and an odd one. Before long they are working alongside a Mossad agent, which makes for some enjoyable friction, since the Cold Case Unit is used to being the awkward outsiders in any room.

Declan Croghan and Barbara Machin wrote it, Tim Fywell directed. Trevor Eve leads as 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. The Dusniak family gives the historical side its faces: Sophie Tait as Bernadetta, Andrew Armour as Marek, Ania Sowinski as Adriane, with Richard Klvac playing Marek as a young man.

Part one of two does what good first halves do. It lays out the 1945 murder, plants the survivors and their silences, and lets the modern team start pulling threads that clearly lead somewhere uncomfortable. The title refers to the memorial candle lit each year for the dead, and the episode wears that idea quietly rather than waving it about.

There is something fitting about the case surfacing through renovation dust. Old buildings keep old crimes, and London has more of both than it likes to admit. The team just has to work out who wanted this particular grave reopened, and why they waited a lifetime to post the evidence.