Dark Matter

Andrew Crompton, amateur astronomer and Master of Gresham College, is found dead at the foot of the University Observatory stairs. It could be an accident, but the show knows better. Suspicion spreads across the college like a stain, touching everyone from the tutors down to the head porter and the college scouts, and Lewis and Hathaway find themselves investigating an institution that has closed ranks behind a facade of politeness.

The case turns on two puzzles. There is the college-wide blackmail plot Lewis uncovers, which gives almost everyone a reason to want Crompton quiet. And there is an astronomical conundrum that keeps nagging at him, a detail in the victim's life that does not fit. Meanwhile Dr Hobson gets pulled into the affair sideways, drawn in while rehearsing with a local orchestra at the college, and her perspective proves useful in unexpected ways.

But the blackmail plot spreads the guilt so widely that the astronomy almost gets lost, which is surely the point: a whole college had reasons to want Crompton quiet, and the stars were the least of it. The conundrum still matters, though, and it is the detail that finally unlocks the case.

Colin Dexter and Stephen Churchett wrote it, and Bille Eltringham directed. Warren Clarke plays Roger Temple, Christopher Bowen is Professor Crompton, Sophie Ward plays Isobel Crompton, Robert Hardy takes Sir Arnold Raeburn, Deborah Cornelius plays Dr Ella Ransome, Diana Quick is Gwen Raeburn, Ruby Thomas plays Kate Cameron, Anthony Calf takes Malcolm Finniston and Jonathan Cullen appears as Father Francis. Clare Holman, Kevin Whately and Laurence Fox anchor the regular cast.

The closed community makes for a satisfying puzzle, with suspects thick on the ground and the truth genuinely hard to spot among them. The observatory setting does its part, all that sky and silence making the small human betrayals feel larger. It is the kind of case where the answer is hiding in plain sight, and the fun is watching the detectives walk past it a few times first.