Sins of the Fathers (1)

DCI Sarah Turnbull is out for blood. Her friend Nick has been murdered, killed while working undercover inside a far-right militia group run by Jason Philpott, and she intends to have the people responsible. The investigation pushes her into uncomfortable corners. But Philpott's people have connections that reach into the official world.

Special Branch turns up with incriminating footage of Danny Kane and uses it to make him comply. Danny is left to work out whether he can trust them, and the episode's tension comes from that question. He plays along, the way he plays along with everyone, and the audience is left to decide who is using whom.

The blackmail is the engine. Danny has spent the series being the man who knows where the bodies are buried; now somebody has footage of him and a lever to pull. Special Branch hold the footage the way other people hold aces, and they play it slowly. The shift suits Leslie Grantham, who has always played Danny best when the confidence cracks a little.

The police world closes in on itself. DI Fairweather, DC Milligan, DS Fielding, DCS Graham and the rest keep their faces straight and their files close, while Frank watches his brother get pulled further in. The episode has the feel of a building with all the exits watched.

Murray Smith wrote it, Gabrielle Beaumont directed. Caroline Bliss's Turnbull, Don Henderson's Frank, Leslie Grantham's Danny, Barbara Wilshere's Carol, Leon Herbert's Polish Joe, Peter Gowen's Jonjo O'Brady, Frederick Warder's Graham, Nigel Harrison's Fielding, James Saxon's Fairweather and Pete Lee-Wilson's Milligan carry it.

This is the first half of a two-parter, and it does the job of a first half: it tightens the knot and leaves you waiting for the second. It is a setup episode that respects its own job, ending on the moment where everything is poised to fall.