Episode 2

Word reaches the Grid that boys and young men from a Birmingham mosque are being trained as suicide bombers. The first problem is the obvious one: somebody has to go in undercover, and the list of volunteers is shorter than the list of reasons not to. And the second problem is the detail that makes it worse. The police have found large-scale fraud around the same mosque, with charitable funds quietly redirected into private bank accounts. Charity money funding terror, with the terror hiding in plain sight behind the charity. The two crimes prop each other up. And the fraud gives the story its entry point: money is easier to follow than conviction.

The script is careful about who the villains are, putting the blame on the recruiters while keeping the wider community out of it. Who goes in, and who can go in without burning the operation or their own cover? The question hangs over the hour, and the answer, when it comes, has consequences. The episode lets the suspense build the old-fashioned way, in rooms full of people saying less than they mean. The best scenes are the ones where everyone is being polite and nobody believes a word of it.

Howard Brenton and David Wolstencroft wrote it, with Bharat Nalluri directing. Keeley Hawes's Zoe and Megan Dodds's Christine Dale are among those in the frame, Peter Firth's Harry runs the room, and Kammy Darweish's Mr. Hussain and Enzo Cilenti's Carlo Franceschini add colour of very different kinds. Jenny Agutter's Tessa Phillips and Heather Cave's Maisie Simm keep the series' regular faces in view. Rene Costa's Cafe Punter, Gary Bakewell's Uniformed PC and Sam Bond's Vinny give the Birmingham streets their texture.

It's an episode about difficult choices made quietly, and the quiet is the point. The restraint does work that other episodes leave to gunfire.