Halsey Innes and his sister, Gertrude, visit their Aunt Ray, who has leased banker Paul Armstrong's home for the summer. They are joined by Gertrude's fiancé, Jack Bailey, an employee of Armstrong’s bank. At 3:00 AM, the house is awakened by a gunshot, and Arnold, the banker’s son, is found dead at the foot of the circular staircase. Suspicion falls on the absent Jack, who despised the victim. A dazed Louise Armstrong is found hiding the house, although she was supposed to be travelling with her father. Later that morning, Mrs. Watson, the housekeeper, is suffering from an injured arm and is soon hospitalized for blood poisoning. News arrives that the Armstrong bank has failed due to a theft of $1.25 million in securities, and that the ailing Paul Armstrong has died. The guests are then notified that they must vacate the house immediately, but Aunt Ray refuses. When Halsey disappears, police detective Jamieson learns from a tramp that the young man was abducted and hidden in a freight car. At the hospital, the dying Mrs. Watson confesses to shooting Arnold in self-defense after he beat her with a golf club. Meanwhile, Halsey informs Gertrude that Paul Armstrong embezzled from his own bank; Louis then returned home after learning of her father’s betrayal. Aunt Ray accidentally locks herself in a secret room and encounters Paul Armstrong. Detective Jamieson and Alex, the new gardener, pursue Armstrong, who slips at the top of the stairs and falls to his death. Alex admits to being Jack in disguise, then reveals the missing securities he found in the secret room. Gertrude embraces Jack, and Louise embraces Halsey.