A 15-chapter Western serial. The serial involves the mystery of the murder of William Stillman (Wells) and the finding of the heir to his fortune. Silent Joe (Farnum) arrives in an effort to discover the murderer and prove that he is the true heir. He and the heroine Lou (Anderson) have their adventures in the mountainous terrain with its "vanishing trails." They are aided by The Shadow (Orlamond), a demented scientist with his trained dog, and several remarkable, death-dealing inventions.