When bodies are found floating in the River Seine, drained of blood, French police begin an investigation into these seeming "Vampire Murders." A curious journalist is drawn into the mystery as well, but is constantly distracted by the lovely Gisele, who is the niece of the Duchess du Grand. Back at the palace of the Duchess, a mad scientist is draining young women of their blood in order to keep the Duchess, a vampire ringleader, alive.