Sons (1)

The episode turns on Cheryl Hutchins, the WPC who takes on more than she can handle during an undercover job. She stumbles onto a nightclub boss with a sideline in S&M films, and the discovery rattles her enough that she blows the operation. Chappel, for whom the case stirs painful memories of his own, sends her to talk it through with Dr Christina Weir.

That thread runs alongside a nastier one. A videotape showing a high-profile MP with two rent boys is stolen, and a blackmail scheme starts up to force its return. As the filming keeps going, Chappel becomes fixed on pulling the two young men clear of what he takes to be an S&M filmmaker and a paedophile. He wants to use what they tell him to bring down other suspected paedophiles working the area. The MP is never named, and the episode is more interested in the men around him than in the headline.

And the personal cost is the point. Chappel and Christina are meant to keep their relationship professional, and they plainly cannot. The job keeps swallowing their boundaries.

Paul Henry Powell, Rob Pursey and Barry Simner wrote it, with Roger Gartland directing. Ken Stott's Chappel is backed by Caroline Catz as Cheryl, David Harewood as Joe Robinson, Marc Warren as Dougie Raymond and Anna Chancellor as Christina, with Tim McInnerny as Max Wilson and Paul Angelis, Eileen O'Brien and Raymond Pickard as the Fitzsimmonds family.

It is a darker, more uncomfortable hour than the two-parter that came before. The show is honest about how Chappel's need to save these boys shades into something close to obsession, and Caroline Catz makes Cheryl's shame feel earned rather than written. Ken Stott plays the obsession quiet, which makes it land harder than a louder performance would. Not an easy watch, and it does not pretend to be.