Edward Derby is a wealthy, sensitive Arkham aesthete who has indulged in poetry and dilettante occultism since childhood. Fascinated by Asenath Waite, he marries her, only to find she is progressively stealing his consciousness.
He appeals desperately to his friend Daniel Upton, but too late. Derby's name and body are ultimately left occupied by an alien mind, the full account reaching the reader through Upton's narration.