Soon after six o'clock on a warm August evening the Ariadne Inn was packed with humanity, and it was not immediately apparent that one of the guests at a table in the gardens was not asleep but dead! There were mysterious elements in the cause of his death and a still greater mystery in his previous activities.
Who was this Mr. Warstock and why had he come to the Ariadne?

Inspector Waghorn breaks a gang of thieves who have found an ingenious way to defraud the Post Office and, along the way, murder a man by poisoning.