While old dogs Jack, Brian and Gerry, and their mistress, Detective Superintendent Sandra Pullman can often find some – usually dark – humour in their work for UCOS (Unsolved Crime and Open Case Squad), there is nothing remotely amusing about their latest case.

No one knew what happened to five-year-old Yasser Blackledge after he went missing 25 years ago, but now paedophile John Davies (Adrian Schiller), fresh out of jail, wants Sandra and her team to believe he snatched the boy and murdered him. Did he, though, or does he just want to go back inside, where he feels safe? Much and all as Davies turns their stomachs, the team reopens the case to find out if he’s telling the truth.

Yasser was abducted from right under the noses of his parents, political activists Anne Gorton (Samantha Bond – Outnumbered) and Fred Blackledge (Kevin R McNally – Pirates of the Caribbean movies). And it turns out they knew Davies, but it could never be proved that he took Yasser. Talking to Anne and Fred, it’s clear they have never recovered from the loss of their son. It would give them some small satisfaction to know that the mystery of Yasser’s disappearance had been solved. But UCOS can’t convince themselves of Davies’ guilt, although they do feel the truth is close at hand.