On a storm-lashed night, Ruth Earlton returns to her father’s crumbling mansion with her fiancé, Ted Clayton, hoping to learn what lingering questions about the Earlton estate will be settled now that her father has died. They are greeted by Ruth’s invalid uncle, Robert Earlton, the housekeeper Mrs. Krug, and the housekeeper’s son, Hanns Krug. In the dark, creaking corridors of the house, Ruth discovers her father's strange legacy: a large ape, a remnant of experiments conducted in the basement, and the unsettling feeling that the fate of the estate is bound to more than just legal papers.
The will is read with a cold practicality: the estate goes to Ruth, but if she dies, it passes to [Robert Earlton]. Small monthly sums are left to the housekeeper and her son, a meager stipend that leaves them resentful and anxious about their future. As the family gathers, tension tightens the air, and Ruth senses that danger lurks behind every corner of the mansion.
That danger becomes all too real that night. Ruth is tormented when a massive hairy hand emerges through her headboard and attempts to strangle her. She screams, and the assault ends as abruptly as it began. Ted and Mrs. Krug rush in to comfort her, and Ted administers a sleeping potion to calm her fear. Ruth drifts into sleep in a chair in her room, while Mrs. Krug stays to guard her.
But the terror returns in the darkness: the same hairy hand reappears and strangles Mrs. Krug. Ruth awakes to a fresh horror and alerts the household to the deadly anomaly plaguing the estate. In the wake of the murders, Hanns Krug confers with Robert Earlton in secret. The two had plotted to eliminate Ruth so the estate would pass to them, but their plan has gone wrong, and Hanns has unwittingly killed his own mother in the process.
As the truth comes to light, Robert Earlton reveals the extent of the conspiracy to Dr. Clayton. Desperate to warn Ruth, Clayton races through the mansion, only to find that Hanns has dragged Ruth down to the basement in a bid to force the ape, Exodus, to kill her. The ape, however, turns on Hanns, killing him instead. The confrontation leaves Ruth frightened but alive, and Clayton arrives to find her safe and sound.
In the tense aftermath, the mansion’s secrets unravel further, and the characters confront a web of greed, fear, and secrecy that has haunted the Earlton estate for years. Ruth faces the reality of her precarious position and the unsettling possibility that power within the house comes at a deadly cost, while Ted remains by her side, ready to protect her from the shadows that still linger in the halls.
