 Ellery Queen and a friend arrive at the neighbouring home in the morning and release the heiress, but by the time they can return her to her home, Marco has been found on the terrace, strangled, and nude except for an enveloping opera cape.The house party and the household contain many people who had good reason to want the victim out of the way, some because he was blackmailing them.As Ellery is investigating the crime, another household member commits suicide out of sheer desperation at the potential revelation of a dread secret.