Dark Secrets

An eccentric elderly couple live quietly and reclusively in Midsomer, asking nothing of anyone. Then a social services investigator is murdered, and their private lives become the most interesting thing in the county. Their house is the sort of place neighbours walk past without quite seeing, and that turns out to be the point. Barnaby and Jones have to work out how much of the couple's oddness is harmless and how much is something darker, which is never an easy line to draw in this series.

William and Mary Bingham are the couple at the centre of it, played by Edward Fox and Phyllida Law, and they are exactly the kind of characters the show does best: perfectly civil, and impossible to read. The social services connection gives the case an uncomfortable edge, because the dead woman's job was asking the questions no one else would ask. Around them circle the Stantons, Eddie, Selina and Verity, each with their own connection to the dead woman. Sarah Barnaby, John's wife, gets drawn into the domestic side of things, and Dr Bullard's expertise is called on as the inquiry tightens.

Michael Aitkens and Caroline Graham wrote it, and Simon Langton directed. Neil Dudgeon and Jason Hughes lead the cast, with Fiona Dolman settling into the role of Sarah, and Edward Fox, Phyllida Law, Neil Pearson, Beth Goddard, Lucy Briggs-Owen and Haydn Gwynne providing the guest strength.

But the show has always had a soft spot for old age with secrets, and this episode indulges it. Nobody looks less like a killer than a frail man in a cardigan, which is precisely why the village keeps its suspicions private for so long. The truth, when it comes, is a reminder that Midsomer's most dangerous rooms are usually the quietest. The mystery is modest in scale and properly nasty underneath, which is exactly right.