The private detective Stas Severin, well known from Sergei Ustinov's previous works, is approached by the daughter of a man brutally murdered by a sexual maniac. A serial killer nicknamed Dame Blanc has been operating in the city for a month and a half. Her infamous "calling card" is a lone playing card on the victim's bloody body. Who is she, how does she manage to elude the police? To begin with, Stas decides to get acquainted with the victim’s surroundings, and then a shocking discovery awaits him: almost everyone he encounters is a semi-finished product for a madhouse. But it seems that the psychiatrist of the strange family is also hiding something very important...