A cinematic portrait of the actress and performer Vija Armane.

Before the end of the Second World War, a special commando marches into a mental hospital located in a beautiful manor house to eliminate the patients. But the Gestapo has received an anonymous letter saying that an enemy agent is hiding among the madmen. Officer Windisch is tasked with finding a simulant among several hundred mental patients in a matter of days.

Roger Mills, a Harley Street specialist, is taking a sailing holiday on the Norfolk Broads. When his six guests find him at the tiller of his yacht with a smile on his face and a gunshot through his heart, all six fall under suspicion.