What is the fa-vourite word in the Channel 4 drama depart-ment? “Edgy”, I reckon. “Edgy” in that way controversy-courting TV people conceive it – like naughty schoolkids, daring to out-rude one other. A few weeks ago, the buzz must have been: “We’ve got this gay drama, Clapham Junction, terribly edgy. Doesn’t show gays as they are. There’ll be a terrible furore about it – but it’s challenging.” “Challenging” is always the defence when programme-makers serve up something toxic: you’re dull, grandad, if you object to being “challenged”.

Forgiven was “challenging” drama, about a wife accepting her paedophile husband back into the family after he admitted abusing their ten-year-old daughter. It was truly shocking. The naturalistic acting of Lucy Cohu as Liz, the wife, and Derek Riddell as Stephen, her husband, was so faultless it was as if we were watching reality. Indeed the story was true. “Liz” occasionally spoke directly to the camera.

It began with scenes of happy middle-class life: the children had an early tea; the parents had a dinner party. Liz told us Stephen’s job was to monitor child pornography on the internet. This was a portent.

Sophie told her mother that Stephen had interfered with her. “I want daddy to stop,” she said. “He will do darling, I’ll see to that,” Liz assured her. You assumed she would throw him out, and some hideous drama would play itself out. But Forgiven wrongfooted our expectations. Raging, Liz confronted Stephen. In a brilliant scene in the car, in which she rained blows on him, he admitted his crime. But she didn’t throw him out. The uncomfortable truth was that she still loved him.

Stephen, apparently horrified by what he had done, went to the police, yet insisted he had done “nothing to harm” his daughter. When they were together, “it was as if we were the only two people in the world”. He was jailed for six months. Here Forgiven ventured into genuinely new and taboo territory. Liz missed him and wanted to reunite the family.

After he was released, Stephen went to a residential programme for paedophiles. This produced the most shocking scene: in a role-play Thomas Craig (Tommy Harris from Coronation Street) pretended to be Stephen while Stephen pretended to be his daughter reenacting one occasion, at bath time, when he abused her. “I feel really strange,” said Stephen/Sophie, “‘cos I’m naked and he’s got clothes on and he’s bigger than me and he’s my dad and he’s rubbing my genitals and I don’t think that’s right.” Stephen/Sophie broke down with a guttural roar.

This was a horribly memorable scene, but it also signalled a central weakness of Paul Wilmshurst’s script and direction. Forgiven was unflinchingly “real” but somehow denuded of emotion and mess. The drama progressed too efficiently through a horrific moral and personal maze and felt inauthentic in doing so. Liz said that she felt “sick, angry, revolted and invaded” by her husband but sorry for him – “forgiving”.

“It’s a question of will,” she argued. Like us, he didn’t understand why she would take him back. She didn’t really elaborate either, beyond a rueful reference to “for better for worse”. How could you sleep with a man who has admitted fantasising sexually about your daughter while having sex with you? This wasn’t addressed. Nor was the emotional distance from Sophie’s insistence that daddy not be allowed near her to her emphatic desire for his return.

The voice of the disbelieving viewer was taken by a friend of Liz’s. “You are mad. He broke the bloody union when he fiddled with your daughter,” she shouted exasperatedly. Her anger was doubly plausible: Stephen admitted to fantasising about his daughter’s friends, too.

The family reunited. Stephen said that he would watch for “triggers”, bed and bath time were no-go. He promised Sophie that it would never happen again. But when he got up in the night to go to the toilet, Liz waited tensely for the flush and his immediate return to bed. In reality, the family have been back together for two years, apparently. Forgiven was truly “challenging” and as a drama was leagues above Clapham Junction. But it didn’t really answer the persistent questions: How could she take him back? Could he really change? And how could a family live with this?

Out of the box

— 10 Years Younger: Summer Special (Channel 4) showed lots of pictures of the extraneous skin around charity manager Ruth’s midriff, left after weight reduction surgery. Airy narration relayed the plan for yet more surgery to remove the skin. Then a quick skip through her fluctuating weight, new hair and teeth. Plastic surgery was presented as easy-peasy as a trip to the shops. This summer’s key beach accessory is a sarong, it seems.

— Carole – kitchen-hogging, sour-faced – deserves to go from BB8 tonight rather than Gerry, the target of her constant bullying and sniping. The public vote will select the two housemates up for eviction, then the ultimate decision rests with the other housemates. Join us to debate the merits of the Greek hunk with a nice line in pants at timesonline.co.uk/bigbrother.

Editor's choice

• U2 at Nou Camp Stadium, Barcelona
• The 50 Best Movie Villains
• The 15 golden rules of theatre etiquette