Episode 4

The bomb is the easy part. Lucas North's former torturer, Oleg Darshavin, walks in with intelligence about a device planted somewhere in London, and Darshavin will only deal with Lucas. Harry suspects the man still holds a grip on him, the kind torture leaves behind, and he is probably right. But the clock does not care about Harry's misgivings: take the intelligence, save the city, and let Darshavin back into Lucas's head as the price of admission.

What follows is really a race against Lucas's own history; the bomb just provides the deadline. Every scene with Darshavin is weighted, and the show trusts Richard Armitage to carry the part of it that happens inside. The hour asks whether a man can face the person who broke him, with innocent lives as the stakes, and it earns the question the slow way. There are no easy outs for Lucas, and the script refuses to hand him one.

David Farr and David Wolstencroft wrote it, and Sam Miller directed. Emil Hostina's Darshavin is properly unsettling, the sort of calm that does not reassure. Hermione Norris's Ros, Genevieve O'Reilly's Sarah Caulfield and Nicola Walker's Ruth Evershed work around Lucas, with Peter Firth's Harry watching him closely. Brian Protheroe is Samuel Walker, Gerard Murphy is Boris Gulyanov, Shazad Latif is Tariq Masood, and Laura Pyper is the Young Woman.

The show has spent years building Lucas's past into a weapon, and this episode finally points it at him. The device is the excuse; Darshavin is the point, and the hour understands that the two are not the same threat. It leaves Lucas exactly where the season wants him, staring at what he came back from. It is the rare bomb episode where the psychology outruns the countdown, which still matters; it just has to wait its turn.