Jane McDowell

In In the Teeth of the Evidence, all that was left of the garage was a heap of charred and smouldering beams. In the driving seat of the burnt-out car were the remains of a body.... An accident, said the police. An accident, said the widow. She had been warning her husband about the danger of the car for months. Murder, said the famous detective Lord Peter Wimsey - and proceeded to track down the killer.

Book 14 in the Lord Peter Wimsey mysteries.