In 1918, in a small town, handyman Howard Wilton finishes a repair on a house and calls out to his employer, Mrs. Warren. Getting no response, Howard prepares to go, then checks inside a closet, where to his horror, he sees Mrs. Warren's dead body. Howard runs from the house, jumps on a train, and eventually ends up in another small town. There, he is hired by Mrs. Helen Gordon, a war widow who needs her large Victorian house cleaned before the upcoming Christmas holiday. Upon arriving at the house, Howard meets Walter Armstrong, Helen's boarder, who is leaving on vacation. Once alone, Howard sets about polishing the floors, but soon recalls Mrs. Warren and becomes distracted. Among Helen's knickknacks, Howard spies a photograph of her husband dressed in a military uniform and turns it face down in disgust. He then goes upstairs to store his overcoat in Helen's cedar closet, while she telephones the grocer with an order. When he comes back down, having heard the last few words of the phone conversation, he nervously asks Helen if she is satisfied with his work. Helen reassures him and suggests that she might hire him on a regular basis. Howard smiles at the prospect but then grows morose, commenting that no one ever asks him back. Sensing Howard's disquiet, Helen encourages him to discuss his problems, but he refuses. Despite feeling dizzy, Howard returns to his floor polishing, while Helen goes upstairs. Soon after, Helen's teenage niece, Ruth Williams, bursts in. When Howard ignores her flirtations, Ruth taunts him about the unmanliness of his job. Infuriated, Howard locks the front door after Ruth departs and pockets the key. Helen then comes down and, seeing Howard's confusion, suggests that he is too ill to work. Helen's concern angers Howard, who reveals that he was rejected for military service because the doctors ruled him mentally unfit. Howard confesses that he has frequent memory lapses and visions of dead people. When Howard admits that he sometimes wonders if he may have killed the people, Helen, frightened, heads for the front door. Howard stops her, but denies he locked the door or has the key. After Helen manages to calm him, Howard asks if he can stay with her for a couple of weeks. Helen says no, stating that Armstrong will soon be returning, but promises to ask her boarder about giving up his room. Howard, who has already forgotten about Mr. Armstrong's vacation, falls for Helen's trick and agrees to leave. While Helen is upstairs retrieving Howard's coat, however, Harold Franks, a friend of Armstrong, shows up, inquiring about the vacated room. Howard tells Franks it has been rented, relocks the door and yells at Helen for lying to him. Howard orders a crying Helen to the kitchen, refusing to let her answer her phone when it rings repeatedly. In the kitchen, Helen breaks a window and tries to escape, but Howard drags her back to the living room. Just then, some neighborhood children show up at the door with Christmas presents for Helen. To avoid suspicion, Howard forces Helen into the basement, then tells the children that she is sick. As the children are leaving, Helen calls out to one through a window, but he does not hear her. Later, a now tranquil Howard brings Helen up to the living room and proudly shows her how he has trimmed the Christmas tree. Howard then suggests they eat, and while in the kitchen, talks about his loneliness. Taking advantage of his mood, Helen announces that he can have Armstrong's room but says she must tidy it first. Howard follows Helen upstairs and, after donning her husband's army coat, tries to kiss her. Although she pulls away, he accepts the rebuff and thanks her for her kindness. At that moment, Doug, the grocery delivery boy, arrives with her order, and Helen tries to slip him a note. Howard catches her, however, and after sending Doug on his way, stalks her in angry disbelief. She runs upstairs to her room and grabs some scissors, but he disarms her. As he threatens her with the shears, she faints, and he momentarily blacks out. Upon reviving, he assumes Helen is dead and rushes off. Sometime later, Helen awakens and goes downstairs. There, she finds Howard about to leave, having forgotten everything that occurred that day. He returns the key and is on his way out when Mr. Stevens, a telephone repairman, shows up. After insisting that the phone is fine, Helen persuades Stevens to give Howard a lift. Once Howard is safely outside, Helen informs Stevens that Howard is insane and was holding her prisoner. While Helen is showing Stevens the broken kitchen window, Howard returns to retrieve his coat upstairs. Unaware that Howard is inside, Stevens goes to his truck, then frantically reports that Howard is missing. After Stevens drives off to search for Howard, Howard comes down with his coat, startling Helen. To Helen's great relief, Howard is still calm and walks out the door with a gentle goodbye.