A strangler is killing Manhattanites, seemingly at random. The only common thread is the unusual silk cords that are used for the killings; blue for men and pink for women. Other than that, the victims come from all social classes and backgrounds, ethnicities, races, neighbourhoods, etc. The city is in a panic. Ellery Queen forms together a small group of people related to some of the victims, and some consultants, and works to determine the killer's reason for selecting these particular victims. When he finally realizes the thread that connects the victims, the murderer is revealed and peace returns to the city.