On the October 1892 night, the Glandier Castle, a little after midnight, while Professor Stangerson works in his lab with his servant, he hears in the room next door the calls of his daughter. Both men hurry, but the door is closed from the inside, just like the shutters of the only window. When they finally discover the young girl gasping on the floor, there's only a bloody handprint on the wall left by the murderer, and the servant's gun: an incomprehensible murder that the reporter Joseph Rouletabille is going to solve.