Episode 8

The mole is in custody, which sounds like progress until you hear what he brought with him. The information Lucas carried back from Moscow points at a thermonuclear device meant for central London, and the Russians are willing to trade the identity of every sleeper agent in the UK for protection and a relocation package for their man. They have also made plain what happens if the deal fails: Harry Pearce dies, and so does everyone in Section D. It is an offer with the generosity of a trapdoor, generous on paper and poisonous in practice, and the Russians know it.

That leaves the team with one source of help, and it is the traitor in their own ranks. So they march him through London, with Russian agents hunting them street by street, trying to reach the codes and the bomb in time. Harry goes to meet his Russian counterpart in person, largely so the other side understands that they all die unless they work together, which is about as close to friendship as this show ever gets.

Neil Cross wrote it, and Sam Miller directed. Kevin Fuller's Walter Crane, Peter Firth's Harry, Richard Armitage's Lucas, Hermione Norris's Ros and Miranda Raison's Jo do the running, with Hugh Simon, Gemma Jones, Kenneth Bryans and Anastasia Hille holding the edges. Robert Glenister's Home Secretary looks on, as Home Secretaries tend to.

But a bomb plot is usually enough for one episode. Here it is almost the least of it, because the hunters and the hunted are the same small group of people, and nobody is sure which role they will be playing by the final scene. The hour earns its tension the honest way: nobody, the team included, knows who gets out. It leaves the big questions unanswered, which is the honest thing for an episode this deep into its own paranoia to do.