The British Secret Service, working to uncover a large-scale blackmail ring and catch its mysterious mastermind, 'The Spider', find themselves at the country residence Feltham Abbey where a fancy-dress ball is in full swing. In the tumult of revelry, Sir Ralph Feltham is found dead. Not the atmosphere bewildered guest Tony was expecting, he sets out make sense of the night's activities and the motives of the other guests. Among them is Hilary, an independently minded socialite still in her...

Ellery Queen is persuaded to accompany an old friend and sculptor to his ancestral home when the latter arrives at Ellery's house covered in blood and unable to remember anything from the past few weeks. Once there, tensions erupt and foul play results in the murder of one of the household's members. Among the many transgressions Ellery will uncover are adultery, blackmail, and deceit.