Tragedy at Law follows a rather self-important High Court judge, Mr Justice Barber, as he moves from town to town presiding over cases in the Southern England circuit. When an anonymous letter arrives for Barber, 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. Enter barrister and amateur detective Francis Pettigrew, a man who was once in love with Barber's wife and has never quite succeeded in his profession - can he find out who is threatening Barber before it is too late?