David Ellington is on a walking trip of Europe following WWI when he gets caught in a storm. He finds a remote hermitage, but is turned away. After he passes out, the monks are forced to take him in.
After reviving, he hears a howling that the brothers say they do not hear. Following the sound, he comes upon a cell with an old man locked inside. The old man says he is being held captive by Brother Jerome, who is insane. After confronting Brother Jerome, he confesses that he is holding the old man prisoner, but the old man is actually the Devil!
Ellington promises to keep this secret, but as soon as he gets a chance, he returns to the cell. He finds that the only thing keeping the prisoner locked up is Brother Jerome's staff. Ellington asks why he never lifted up the staff himself. The prisoner doesn't give a clear answer but one of the monks arrives at the door. The prisoner says that Ellington must hurry. Ellington does so. He lifts the staff and releases the man, who proceeds to transform into the Devil and disappears in a cloud of smoke and fire. Shortly after, WWII breaks out.
Ellington devotes his life to recapturing the Devil. He finally does recapture the Devil. As he prepares to leave to make arrangements to ship him back to the hermitage, he tells his housekeeper to pay no mind to the howling. But, as soon as he leaves, she lifts the tiny staff on the door, and the door swings open.