The mutilated body of a man has been found near Durnkrut. Jules Brandt, the detective, is informed at the same time of a mysterious airship which comes and goes. He resolves to stay in the village on the border of the forest. The next time the airship appears he gives chase after telephoning M. Charles Illner, the Austrian aviator, who joins in and they fellow the airship to its shed. There Brandt learns of the sudden disappearance of a young American, James Stirner. He is shown a picture of Stirner which is that of the mutilated man. He visits Stirner's villa and finds a torn bit of paper containing these words: "I cannot bring myself to do it, and I beseech you not to disturb the peace and quiet of our home." The detective introduces himself to the aeronaut's wife, Marie Weyer, and gives her to understand the nature of his investigations. Terrified, she confesses to him that unwelcome attentions had been paid her by Stirner after her marriage to the aeronaut. Hoping that the wealthy young American would finance the building of the airship, she had written him that she would visit him to plead her cause. She did not go, but the American held the letter over her head after as a threat. When the airship was completed, Stirner jumped aboard with the aeronaut and his wife and later, when her husband was busy with the rudder, he rushed at Marie, whose screams were drowned by the sound of the machinery. The pair struggled, Stirner lost his balance and fell. Max saw nothing of the tragedy. At the completion of the story the detective expressed his sympathetic understanding by leaving the young woman and her husband undisturbed.
—Moving Picture World synopsis