Fulfilling a promise made to his mother on her deathbed, Dr. James Gibson finds his sister Pauline who has run away after giving birth to an illegitimate child. His sister's mind has snapped and Gibson takes his sister and his baby niece home with him. The years pass and the niece has grown into a beautiful woman while her mother is kept locked in a room that the young woman is forbidden to enter. Gibson and his wealthy neighbor, John Morris, are both interested in hypnotism, and one night the two men conduct an experiment by hypnotizing Gibson's niece. Pauline sees Morris from her window and recognizes him as the man who deserted her after fathering her child. One night she escapes from her room, takes her daughter's shawl, and stabs Morris to death. Returning home, she touches her daughter's hair, leaving blood stains on the sleeping girl. Morris is found murdered, the young girl's shawl is found near his body, and his blood is found on the still sleeping girl. The niece is arrested...