Aunt Ray Innes leases Sunnyside House, the country home of Paul Armstrong, and invites her nephew and niece, Halsey and Gertrude Innes. En route, the young people stop at the Greenwood Club to take Jack Bailey, the intended husband of Gertrude and cashier of the Armstrong Bank. Halsey appears in time to prevent a fight between Jack and Arnold Armstrong, son of the banker. At three o'clock in the morning a pistol shot awakens Aunt Ray, who summons her servant, Liddy. They are joined by Gertrude, and the women discover that Halsey and Jack are missing. Investigations disclose the lifeless body of Arnold Armstrong lying at the foot of the circular staircase. Mr. Jarvis, who had been summoned from the club, recalls that Jack and Arnold were bitter enemies because of banking affairs. The next morning Mrs. Watson, the housekeeper, appears suffering from an injured arm, which she explains she sustained in falling down the circular staircase. Frank Jamieson, the detective, on the case cannot trace Jack, and when Halsey Innes returns he refuses to say why he left. Then the newspapers announce that the Armstrong bank has failed; that the cashier has been released under bond; that Dr. Walker, who has accompanied Paul Armstrong to the west, has wired that the banker is too ill to travel, and that securities aggregating a million and a quarter are missing. Aunt Ray searching for Tom, the butler, comes upon Louise Armstrong, daughter of the banker, who was supposed to be out west with her father, at the Lodge. Dr. Stewart, the family physician, attends to her. Dr. Walker wires that the banker has died, and that his summer home must be vacated as the body will arrive soon. But Aunt Ray refuses to leave on such short notice. Louise is not apprised of her father's death, and as she leaves for her mother's home she tells Aunt Ray to leave Sunnyside House, as she has forebodings for its future. Mrs. Watson's injuries develop into blood poisoning, and she is taken to a hospital. As Tom, the butler, sits in the Lodge one night, he sees an apparition and drops dead of fright. Dr. Walker warns Aunt Ray to leave the house before she regrets it. Again she refuses. Several nights later as Halsey and Alex, the new gardener, are keeping watch over the circular staircase, the stable catches fire, and the men rush to give assistance. Meanwhile the women are terrorized by the movements of a strange object outside. Halsey disappears and a tramp with the missing man's watch on him is caught by Detective Jamieson. Upon being questioned, he says that he found the watch under the freight car into which had been thrown Halsey, bound and gagged. Mr. Watson, who is dying, tells Aunt Ray that when she was carried to the lodge by Tom, the butler, she found Louise Armstrong ill and that she (Mrs. Watson) was struck on the arm by a golf club by Arnold because she refused to give him the key to Sunnyside House. Mrs. Watson returned to the house and when she was ascending the circular staircase found that Arnold was creeping up behind her and shot him. Gertrude learns from Halsey, who is in a neighboring hospital, that Paul Armstrong, aided by Dr. Walker, looted his own bank, and that is why Louise left her father. Meanwhile the casket containing Paul Armstrong's body is exhumed and when opened it is found that the corpse is not that of the banker. Aunt Ray discovers a secret room and upon investigating she is locked in by the door automatically closing upon her. Here she is found by Paul Armstrong that night. The sight of him frightens her and her cries bring the detective and Alex, the new gardener, who break open the door as Armstrong escapes by another secret passage. He slips down the circular staircase and is killed, and Dr. Walker is taken into custody. Alex removes his disguise and reveals himself as Jack Baily. A cash box containing the stolen securities is found in the secret room by Jack, and as Aunt Ray comes into Sunnyside House she finds Louise and Halsey in a loving embrace, and Jack and Gertrude in a like attitude at the bottom of the circular staircase.