Trapped at the bottom of a cistern on the estate of Sans Souci, David Cummins reflects on the circumstances that led him to be imprisoned there: A week earlier, David is arrested for vagrancy and sentenced to thirty days in jail. Lawyer Philip Cagle pays his fine and offers him $500 to pose as a man named Malcolm Taylor. Cagle tells David that he greatly resembles Malcolm, who has been missing for almost seven years and is about to be declared dead. For reasons of his own, Cagel wishes to prevent that. David agrees to the masquerade, providing that Cagle pays him $5,000. David's act must convince Calder, Malcolm's brother; Calder's wife Nadine; and Malcolm's wife Evelyn, all of whom live at Sans Souci, and his arrival at the Taylor estate is a shock to all three. During the following days David learns that both Calder and Evelyn hate Malcolm, and that Nadine had an affair with him. Privately, Nadine tells David that she stayed with Calder for the money he would inherit if Malcolm did not return. Later, as Malcolm, David apologizes to Evelyn for hurting her, prompting her to assert that he is somehow changed. The following morning, Cagle advises David to protect Evelyn from Nadine's schemes. Later, Nadine notices that David does not have Malcolm's distinctive scar on his arm and accuses him of killing Malcolm in order to take his place. Nadine then threatens to reveal the deception unless he agrees to split the inheritance with her. After David tells Cagle of this conversation, Cagle secretly meets Nadine, with whom he is scheming to kill Evelyn for the inheritance. Realizing that Nadine knows David's identity, Cagle pushes her over the cliffs. After Nadine's body is discovered, Cagle warns David that the investigation into her death will expose his imposture and asks him to pretend to sign a paper leaving the estate to Evelyn before he goes away. Cagle and David then leave together, but before they are off the estate, Cagle pushes David into the cistern and leaves him to die. When David comes to, he finds an identification bracelet belonging to Malcolm and realizes that Cagle killed Malcolm just as he has tried to kill him. While David is in the cistern, Cagle returns to Sans Souci and hints to Calder that Evelyn killed Nadine. Calder then tries to push Evelyn off the cliffs. Meanwhile, David has managed to crawl out of the cistern, and hearing Evelyn scream as she struggles with Calder, hurries to her rescue. During the ensuing fight, Calder falls to his death. David then confronts Cagle, who flees and falls into the cistern to his death. After David tells the entire story to the sheriff, he and Evelyn make a new start together.