A young reporter solves a mystery crime. The fictional reporter is Joseph Rouletabille. He works on a complex, and seemingly impossible, crime in which the criminal appears to disappear from a locked room.

Mathilde Stangerson just married her fiance, when she heard that Larsan, her cruel former husband, whom she believed to be dead, is actually very much alive. Taking refuge to her castle, she appealed to the journalist Rouletabille to protect her.