Margery, the adopted daughter of Hon. Carter Breene, becomes acquainted with Allen Dare, much to the displeasure of Darrell Shane, who has an affection tor the girl. That evening Arthur, the profligate son of Breene, comes home under the influence of a drug, and in the presence of Shane, Dare, Peters, Breene’s servant, the father has a new will drawn up which bequeaths everything to Margery. As Breene sits in the darkened room by himself, he is mysteriously murdered. Peters gives the alarm; the police are summoned, and upon the demands of Shane, Margery, who had previously visited her father and who had tried to awaken him from what she supposed to be a sleep by drawing her scarf over his face thereby getting blood stains on it, is arrested. Shane also orders Dare’s arrest, but he manages to escape to his car, which is covered in black cloth. At a fork in the roads, Dare, heavily masked, overtakes the police auto carrying Margery, and at the point of a pistol, gets the girl into his car, and speeds away to his home. As Dare’s servant, Hodge, is removing the black covering from his master’s beautiful white car, a stranger with a white mask jumps out, unobserved, from the auto, runs and disappears. The next day the coroner’s jury finds Margery guilty of the crime. That night, as Dare, masked, and his car again shrouded in black, goes to the home of Breene to secretly secure evidence, the mysterious stranger in a white masks effects an entry into Dare’s home, where Margery has taken refuge, and confronts the girl who faints. The masked man then sets a trap which, in the event of the door being opened, will result in the girl’s death. Meanwhile Dare, who has found an opium pipe with bloody finger marks on it in the room where Breene was murdered, returns to his home just as the stranger is leaving. Instead of following him, Dare gains egress into Margery’s room through a window. He releases the girl from the trap, and finds another opium pipe with finger marks on it which compare with those on the pipe he found in Breene’s home, and concludes that the owner is the murderer. Shane puts into effect the suggestion, to raid Dare’s house, that he received in an anonymous letter, and while this is taking place, Dare, oblivious to the raid, goes to Breene’s home to secure more evidence. As he is searching the room in which the murder was committed, he is confronted by the stranger with the white mask, but before Dare can get hold of him, the stranger makes his escape through a window. Margery has been taken from Dare’s house by Shane’s raiding party and sent off to town with a set of officers. Speeding away on his motorcycle, Shane reaches a point where the roads diverge. The road on the left is blocked with a sign “Cliff Road, Dangerous.” This he removes and puts across the road to the right. The police car turns to the left. They see the cliff too late and in a moment are dashed over it and into the lake below. Dare, who has been following, steps from his car, removes his cloak, cap and mask and dives into the water. He comes up with Margery, and takes her in his car to her home. The white masked man returns to the Breene library. Suddenly a vision of Breene rises before him. In a frenzy he beats on the chair over which the apparition appears. The noise attracts Peter who fires upon the intruder. Dare and Margery arrive just as the shot is fired. As they enter the library Peters removes the mask of the prostrate man. It is Arthur. At this juncture Shane and two officers also arrive. Arthur then confesses that it was he who killed his father. Shane, non-plussed, leaves with his men. Margery turns and thanks Dare. Silently he looks into her eyes, then turning about he hurries to his car and drives off, Margery watching him as he fades into the distance.