Francis Pettigrew travels to Exmoor for a holiday with his wife - an area in which as a young boy he was traumatised by coming across a dead body on the moor. In an attempt to exorcise this trauma, Pettigrew walks across the moor to the place where the incident occurred - only to find another dead body.

When an anonymous letter arrives for Mr Justice Barber, the High Court judge, warning of imminent revenge, he dismisses it as the work of a harmless lunatic. But then a second letter appears, followed by a poisoned box of the judge's favourite chocolates, and he begins to fear for his life.

Famous solo violinist Lucy Carless is making a guest appearance with the provincial Markshire Orchestra, only to be found strangled with a silk stocking part-way through the concert. Everyone in the orchestra had access to the scene of the crime, and the police officer in charge, Inspector Trimble, has no idea where to start.