Fearful Symmetry

A pretty graduate student moonlighting as a babysitter is found bound to a bed and smothered. Jessica Lake was leading two lives, the domestic one and a private one that involved posing for provocative bondage photographs, and the discovery of that second life reshapes the investigation. Lewis and Hathaway follow the trail into an elaborate swingers' network, a hidden Oxford of discreet arrangements and complicated couples.

The central question the detectives have to answer is whether Jessica's death grew out of that secret world or out of something older: her time spent in a children's home. She might have been targeted, or she might simply have been an unintended victim of forces that had nothing to do with her at all. The episode keeps both possibilities alive for a long time, and the sifting through private histories is done with more sympathy than judgement.

But the episode is careful not to judge the swingers' world it uncovers; the judgement falls on the violence rather than the lifestyle. Jessica's two lives never quite met, and that gap is where the killer moved. What unsettles is how ordinary arrangements can hide extraordinary cruelty.

Colin Dexter and Russell Lewis wrote it, and Nicholas Renton directed. Abigail Hardingham plays Jessica Lake, Georgia Taylor is Honey Addams, Ciarán McMenamin plays Nick Addams, Lucy Cohu takes Marion Hammond, Gregor Truter plays Dr Joshua Ezrin, Con O'Neill is Dr Bob Massey, Katrine De Candole plays Davina Garland and Gary Kemp takes Tom Garland. Kevin Whately and Laurence Fox lead, with the usual supporting depth.

There is a genuine discomfort to this one, the polite city revealing an organised secret life underneath. The episode handles the material carefully, more interested in why than in gawping, and the ending leaves a couple of questions deliberately open. Some victims, it suggests, stay a mystery even after their killers are found.