One afternoon, Frank Thompson is knocked unconscious by wreckage falling from a building on Tillary Street in New York City. When he revives, Frank is seriously disoriented although unharmed. Frank soon discovers that his apartment has been rented out for a year and his wife Virginia has been living on her own elsewhere. Frank confronts Virginia, who is shocked to see the husband who disappeared without explanation a year earlier. Virginia is thrilled to reunite with Frank, who has no memory of the past year, and he returns to his regular life. Soon, however, he is haunted by the appearance of Joe Marucci, a threatening looking police detective who follows Frank everywhere, and eventually breaks down the door to the apartment to arrest him. Frank and Virginia escape on the rooftops and he sends her home to her mother until he can clear up the mystery behind his missing year. By returning to Tillary Street, Frank hopes to jog his memory and is startled when Ruth Dillon, a beautiful blonde, hurries him into her apartment for his own protection. Ruth identifies Frank as her lover, known as Danny Nearing, with whom she worked as a servant at the Diedrich estate in Jericho County until Frank was accused of Harry Diedrich's murder. Convinced that he is innocent, Frank insists that Ruth accompany him as he searches the Diedrich estate for evidence. Ruth reluctantly accompanies him as he probes around the dark house. There Frank discovers that Grandma Diedrich, an elderly, mute invalid, witnessed the murder but was not consulted by the police. Harry's wife Alma and her lover, his brother Bill, return from an interrogation by the district attorney and are surprised to find Ruth in the house on her day off. Frank hides in the greenhouse while Ruth cuts the phone wires so that the suspicious Diedrichs cannot call the police. The next night the Diedrichs go out and, unknown to Ruth and Frank, Joe watches their activities. Frank gets a few moments alone with Grandma and communicates with her through a code they have worked out with eyeblinks. Frank is shocked to learn from Grandma that Ruth is the real killer. When pressed, Ruth admits that she unintentionally stabbed Harry when he found her stealing money. Despite Ruth's pleas, Frank is unable to sympathize with her because she selfishly let him suffer the burden of the murder accusation in order to save herself. Ruth tries to kill Frank, and as they struggle for the gun, a shot is fired into Ruth. Joe comes into the house after the shot is fired and hears Ruth confess to the murder before she dies.