Guy Fawkes Night, 5th November, 1930. Bonfires are blazing, rockets burst. In a country lane, revellers discover a car that has been set on fire. At first, they assume that this is the work of vandals taking the Guy Fawkes spirit a little too far, sitting at the wheel is a body, charred beyond recognition.

The initial assumption is that the owner of the car, Mr Harold Musgrave, a successful travelling salesman has taken his own life in a particularly grisly act of self-immolation. The post-mortem, however, reveals that Mr Musgrave was either unconscious or dead before the fire was lit. When Tommy Prosser, a local criminal, is charged with the murder, barrister Arthur Skelton believes him to be innocent, so sets out to ensure justice is served.