Apocalypse

Someone is murdering opponents and former members of a religious cult, and each killing follows one of the Biblical plagues of Egypt, which the Book of Revelation says will precede Armageddon. The team is baffled, and you can see why. There are more than fifty members of the cult, and most of them would kill if the leader, David Burns, asked. The script borrows the apocalypse talk without buying into it, which is the right way to use a mad premise. The murders are staged to be noticed, which is part of the killer's message.

But the cult's obedience is the real horror. Nicholas Clay plays Burns with the sort of serene authority that makes that obedience plausible. The episode keeps asking who is responsible and who will be next, and it does not answer the first question quickly. The team is chasing a killer who thinks he is doing God's work, which makes the normal rules of motive useless.

The plague-by-plague structure gives the investigation a countdown feel without ever becoming a gimmick. Tony Curran plays Ian Jardine, a suspect who shares his surname with the detective investigating him, a coincidence the show leaves alone. The Burns family is all over the case, which gives the team a short list that keeps growing. There is a genuine dread to it that survives the premise's oddness.

Glenn Chandler wrote it, Marcus D.F. White directed. James MacPherson, Blythe Duff and Colin McCredie lead, with Iain Anders as McVitie and Robert Robertson as Dr Andrews. Nicholas Clay's David Burns, Lorna Heilbron's Martina Burns, Tony Curran's Ian Jardine, Alec Newman's Stephen Burns and James Mackenzie's Keith Burns round out the cult's inner circle.

Cult stories are easy to do badly. This one keeps the menace in the ordinary details, in the people who will kill because they were told to. It is a grim, careful episode that earns its title without overreaching.