Maria van Buren, a beautiful, high-class prostitute, is found dead with a knife in her back in her houseboat on an Amsterdam canal. Grijpstra and de Gier must solve the murder. Her tony clients all have sound alibis. Before the murderer is caught, the detectives and their commissaris will investigate allegations of black magic, travel to Curacao, and pursue clues to a chilly island off the coast of Holland.