Black Shadows (1920)

Marjorie Langdon, heiress Janet Fordyce's chaperon, is suspicious of Janet's admirer Chester Barnard. During a reception at the Fordyce home, hypnotist Professor Potter discovers that Janet is a willing subject and schemes with Barnard, hypnotizing Janet and inducing her to steal jewelry and fence it under Marjorie's name. Marjorie is accused of the crimes, but Duncan Fordyce, Janet's brother, discovers that his sister has perpetrated the thefts under hypnotic suggestion. When Barnard is apprehended in an attempted robbery, Marjorie is cleared and she and Duncan marry.