Ling Foy seizes old Martin’s violin as security for the money which the opium addict owes him. The musician is informed that the instrument will be returned when he settles the debt, or brings two new customers to the joint. Drake, a plainclothes man, is assigned to investigate the Ling Foy den. The detective discovers that Martin frequents the place and later meets Annie, the musician’s daughter. Annie later learns from her father as to what has befallen the latter’s violin and determines to plead with Ling Foy for its return. First, however, Martin endeavors to persuade his old friend, Ludwig, to visit the den. Ludwig indignantly declines the invitation. Drake cunningly contrives to have the musician take him to Ling Foy’s and thus gains admission to the place. The following day, Annie and her father call upon the Chinaman. Fired by the girl’s beauty, the Oriental makes her a prisoner. A similar fate falls to Martin when he attempts to go to Annie’s rescue. At the same time, Drake heads a raiding party and smashes into the den. With the arrival of the police, Ling Foy rushes into the secret room in which he has confined his victim. The girl’s screams bring Drake to the scene and he comes to the rescue. The sleuth and the Chinaman engage in a terrific struggle which ends in Ling Foy’s death. As Drake escorts Martin and Annie to their home, the old musician, his lesson learned, vows never to touch opium again.