Ethel Vandiver and her friend, Marie Le Farve, arrive at the former's country home. Ethel's father objects to her seeing Douglas, whom he thinks is a sweetheart. But, unknown to her parent, Ethel has married Douglas a year before. The day on which she arrives she receives a letter from her husband stating that he would rather see her dead than be separated from her any longer. A few hours later Marie is found dead in Ethel's room. William Sanford, a newspaper reporter, starts to work on the case and the only trace he can obtain of the crime is the imprint of a cloven hoof on the carpet. Detective Huff then arrives and finds Douglas' letter, which convinces him that he is on the trail of the guilty person. Sanford and Douglas are friends and the reporter determines to prove his friend's innocence. That night Sanford goes to the room. He is horror-stricken to see a hand emerge from the door of the clothes closet. He summons Huff, and when the hand again appears, he fires four shots at it. They are unable to locate where the bullets struck and the detective gives up in despair. Sanford discovers a push button that opens a door which leads to a dungeon. In this dungeon he finds Craven, a mulatto gardener, who has been killed by the bullets. The murderer has been discovered; they find that his left foot is a cloven hoof, "the devil's signature." Ethel's father then congratulates Douglas, forgives him and allows him to come and claim his bride.