Frivolous young Mrs. Pensonby Smythe, trapped in a loveless marriage, secretly accompanies the loutish "Billie" Carrington to "The House of the Mask," a notorious gambling palace where the rich play in secret with masked faces. While there Carrington attacks her and she is rescued by gambler Belmont Blair who recognizes her. In the ensuing scuffle Carrington is accidentally killed. Blair gets Mrs. Smythe out of the house before the body is discovered. In time Blair, who loves Mrs. Pensonby Smythe’s sister Grace, sacrifices himself to protect them both.