Dr. James Brent, surgeon and psychologist, receives a strange case in the person of Richard Wayne, a young man who, although upright in all other respects, is obsessed with a monomania for appropriating diamonds. Struck by Wayne's appearance and unfortunate plight, Brent agrees to study his case. He allows Wayne to remain in his house, acting as his private secretary. After a few days at Brent's home, Wayne forms an attachment for Brent's daughter Elsie, who is horrified to see him steal a diamond pin from a guest to their home. She follows Wayne to his room and there learns of his mania. Wayne, heartbroken by the realization of where his trouble is leading him, returns the pin and swears to Elsie that he will fight his strange obsession harder than ever. Dr. Brent has always decried his beloved wife Julia's growing extravagance, and now he holds her to a stated allowance, but she continues her social ambitions, and gives a magnificent ball which plunges her into debt. At the ball one of her guests, Mrs. Gannon, loses a valuable diamond sunburst. Wayne, coming unexpectedly across the gem, is desperately tempted through his strange fascination. Secretly watching him from another part of the room is Julia. Wayne fights down his temptation and leaves the jewel where he found it. Julia, realizing that Wayne will be blamed if the jewel disappears, confiscates it. She sees a chance to emerge from her debts by pawning the jewel. When Brent hears of the jewel's disappearance, he immediately suspects Wayne and calls upon him to give it up. Wayne vehemently denies the accusation. Brent, realizing Wayne's love for Elsie, and now believing that he is either a deliberate thief or a helpless monomaniac, commands him to leave the house; Wayne does so after a heartbreaking farewell with Elsie. He is followed by the private detective at the ball, and next day arrested on suspicion. Julia has pawned the jewel, which is later found at the pawnshop by the detective. At the same moment, Elsie discovers that her mother was the real thief. While she insists that Julia make a confession to Brent, the detectives are on their way to the house to arrest Julia. Julia finally gathers her nerve together and faces Brent in his study with a full confession. Brent has just received a wire from the National Medical Association electing him president of the organization, and the confession of his wife's dishonesty crushes him completely. Mrs. Gannon, the owner of the jewel, who is indebted to Brent through the saving of her life by his skill, intercedes in Julia's behalf. She prevents Julia's arrest, and finally obtains an understanding and reconciliation between Brent and his wife. Wayne has been released from custody and now, thoroughly cured, through Brent's skill and the realization of Elsie's love, goes to her to ask her to become his wife.