While picking up a load of junk, the boys acquire a trunk from an old ship. A journal from a crewman is hidden in the trunk, giving clues to find a treasure that he hid before his death.
While accompanying Pete's inventor grandfather to New York where the old man plans to sell his new invention, the Three Investigators find themselves in the middle of a dangerous spy case.
Wealthy eccentric Charles Barron is convinced that aliens are planning to fly to earth and take him away. The detective trio resolves to prove that Barron is being taken for a ride--but not by hostile aliens.
