A seemingly kind painter, Henry Elcott, tricks wealthy art collector Mary Herries into letting him, his wife Ada and their baby live in her London home.

It turns out to be a diabolical scheme by Elcott to sell off the artwork of Mrs. Herries and everything else of value she owns while holding her and her housemaid Rose captive in their bedrooms.

Elcott masquerades as the lady's nephew, come to take care of her affairs due to a sudden mental breakdown.

The criminals taunt Mrs. Herries, placing her chair near a window, having informed the neighborhood that any screams they hear would be those of a woman who has gone mad.

Tensions rise as Mrs. Herries learns the true identity of Elcott from a portrait of his wife that he signed with his real name.