A young doctor, named John Walthol, proposes to Mary Chalmers, and is accepted. A few days later, when a "medicine show," the principal feature of which is hypnotism, comes to town, Mary and her chum, May, go to see it. The hypnotist introduces himself to the girls, and finally extracts a promise from them to call upon him the next day and have their fortunes told. The doctor remonstrates against their doing any such thing, but nonetheless, they go. While May's attention is attracted, the hypnotist puts Mary under his influence and has her write her fiancé a letter telling him that he need not look for her anymore. Several weeks later the doctor meets May on the streets and upon inquiring for Mary learns that she left with the hypnotist while under his influence. She shows him a letter from Mary saying that while she would like to get home she can't, as she is under the influence of the hypnotist. The doctor leaves at once for the town where the show is and sees Mary, but she does not recognize him. He returns to his room and spends the night studying works on hypnotism. The next day he visits the show, takes a seat in the audience, concentrates his mind on the hypnotist and soon has him under his influence. Mary is brought back to her senses and the hypnotist is arrested.