Commissaire Maubritane is approached by an old acquaintance, Pierre Sertat, who has become terrified by strange noises coming from within his locked and bolted villa, and who fears that the lives of himself, his wife, and his daughter may be in danger. He believes that two smuggling gangs have perfected a technique for passing through walls and will kill him if he divulges any information about them. Against his better judgment, Maubritane agrees to spend the night in the villa. He makes a thorough search of every room, but cannot prevent a mysterious stranger entering and shooting Sertat, who almost dies, and somehow avoiding the commissionaire’s pursuit.

During the following nights and days numerous attempts, some successful and some not, but all seemingly impossible, are made on the lives of the Sertat family. Maubritane fails to prevent them or explain them and thinks he is going mad….