Lieutenant Esmond, a young American officer, invents a wireless operator which successfully proves its ability to destroy hostile warships. Secret agents of foreign governments try unsuccessfully to secure the plans. Heinrick Hoevler, an old German inventor, perfects an instrument capable of reading the thoughts of any person with whom it comes in contact. The existence of this wonderful invention becomes known to an emissary of a foreign government and he arranges with the old inventor to enlist its service. Lieutenant Esmond accepts an invitation to visit the secret agent at his hotel, and, although he realizes that the spy is endeavoring to secure information from him, he feels sure that he has failed, not knowing that although he has not said anything about his great secret that the mind reading machine has discovered and recorded it. When the details of the invention are found to be in the possession of the foreign government, the young lieutenant is at once placed under arrest, and being unable to prove his innocence, he is dismissed from service. His sweetheart, a girl employed in a large hotel as telephone operator, chances upon a clue which enables her to discover the wonderful instrument which had caused the lieutenant’s disgrace. The young officer and the girl make their way to the inventor’s house and there secures the proof that reinstates him in the army and defeats the plans of the foreign government.