Spots 
Signor Ricardo conceals his past as Paolo, Marchese di Sorrento, living in a quiet Soho lodging-house while privately studying occult magic. He confesses his secrets to Dr. Steinberg, revealing how jealousy led him to destroy his wife, Leonora. Meanwhile, the landlady complains of her simple maidservant, Hannah Stubbs, who unknowingly causes household furniture to move.
CHAPTER I. → CHAPTER III.
Dr. Steinberg and Signor Ricardo realize that Hannah Stubbs possesses raw mediumistic magnetism rather than mere hysteria. They pay Mrs. Battleby for permission to conduct regular evening sittings to investigate her powers. Though terrified of the dark cabinet room, Hannah falls into deep trances guided by an unseen masculine voice.
CHAPTER IV. → CHAPTER VI.
Eavesdropping on a séance, Mrs. Battleby mistakes spirit invocations for immoral conduct and summons Hannah's rural family. Hannah's pious mother and fiancé, Joe Brushwood, arrive from Settlefield to accuse her of witchcraft and indecency. Joe breaks their engagement, and her mother disowns her entirely. Cast out by her family, Hannah is left dependent on the two investigators.
CHAPTER VII. → CHAPTER IX.
Regular sittings materialize the coquettish spirit of Leonora, whose claim of innocence fills Ricardo with crushing remorse. Meanwhile, Hannah undergoes an alarming internal change, adopting foreign mannerisms, singing French songs, and demanding control over séances. She sheds her former rustic submissiveness while Ricardo grows increasingly frail and tormented.
CHAPTER X. → CHAPTER XII.
Now elevated in social standing as Ricardo's wife, Hannah attends a lavish evening gathering at Baron von Steinberg's residence. She commands the room with unexpected dignity, startling the guests with her refined demeanor and powerful physical manifestations. Afterward, Steinberg finds himself strangely drawn to her newfound allure, unaware of her growing greed and deception.
CHAPTER XIII. → CHAPTER XV.
Following Ricardo's sudden death from poison, Hannah operates secretly as a paid medium named Mrs. Brown. Entranced by her persona, Steinberg proposes marriage, taking her to Paris where she rapidly acquires high-society polish. Yet beneath her aristocratic facade, Hannah becomes increasingly cold, ambitious, and manipulative, leaving Steinberg torn between intense attraction and growing revulsion.
CHAPTER XVI. → CHAPTER XVIII.
During a séance, the spirit of Ricardo returns to inform Steinberg that Hannah poisoned him with arsenic. When confronted, the woman proudly admits to the murder and reveals the ultimate truth. She is no longer Hannah Stubbs, but the vengeful spirit of Leonora, who permanently seized the medium's body during their early séances to wreak retribution.
CHAPTER XIX. → CHAPTER XX.
Spiritualist obsession invites a vengeful ghost to possess a medium and usurp her life.