The Parasite is an 1894 novelette by Sir Arthur Conan Doyle. The Parasite makes use of a form of mind control similar to the mesmerism of the Victorian era; it works on some hosts but not others.
The main character is a young man known as Austin Gilroy. He studies physiology and knows a professor who is studying the occult. The young man is introduced to a middle-aged woman known as Miss Penclosa, who has a crippled leg and psychic powers. She is a friend of the Professor's wife. The skeptical ...