The Friday Event

A sixth former falls from a roof at a top Glasgow school and the first verdict is suicide. Then a journalist takes an interest, publishes a piece linking the dead boy to drug dealing, much to the headmaster's fury, and turns up dead himself. His affair with the paper's editor makes her the obvious suspect. Then another student dies, and the Strathclyde team has to admit that they're not chasing a run of bad luck. There's a killer at work who's been in plain sight all along.

But the third body doesn't just change the count, it changes the case. The manner of the latest death sends the inquiry in a direction nobody expected, towards a famous painter, and the team is left juggling media pressure, grieving parents and a pattern that stays maddeningly out of reach. A killer who operates in a school, the episode keeps reminding you, is someone who likes being underestimated.

Glenn Chandler, Ann-Marie di Mambro and Stuart Hepburn wrote it, Ian Madden directed. Blythe Duff is DS Jackie Reid, John Michie is DI Robbie Ross, Alex Norton is DCI Matt Burke, Colin McCredie is DC Stuart Fraser and Anne Marie Timoney is DSI Valerie Patterson. John Kay Steel plays Eddie Drummond, Deirdre Davis is Melanie Drummond, Ian Cairns is Michael Morrison, John McGlynn plays Danny Morgan and James Young is Darren Drummond.

An apparent tragedy spiralling into something far colder is a well-worn route for the show, but this one earns its way there. The school setting gives it an extra chill. Murder inquiries usually come with a shortlist of adults; here the bodies are children, and that changes the temperature of the whole investigation. The headmaster's instinct to defend the school's reputation before the facts are gathered is a small, true detail that says more about the institution than any speech could.