Walter Jason, a young man from the country, comes to the big city to find a position, but fails to do so. Oswald Trumble, so known to society, though in reality a master crook, strolls through the park, his mind busy with a scheme to steal the jewels of Mrs. Crosby Moore, a leader of society, whose forthcoming fancy-dress ball is the talk of the town. As Trumble approaches the bench where Jason is seated, the young man arises, shows exhaustion and then slowly continues on his way. Struck with Jason's clean-cut appearance, Trumble follows the young man, trails him to the river, and prevents him from committing suicide. Later, we find Trumble and Jason, seated together in the grill of a hotel, the latter doing justice to a full meal, purchased by Trumble. Still later, we find Jason in Trumble's apartments, where the latter, under the guise of disinterested friendship, is urging the young man to exchange his shabby clothing for a more fashionable suit. Still later, Trumble introduces Jason into his social set, setting the young man's mind at rest with the explanation that he, Jason, can be of assistance in the disposition of certain bonds, securities, etc., in which Trumble deals. Jason accepts the explanation, also Trumble's money, and makes himself agreeable to those to whom he is introduced. In the course of events, Jason meets Mildred Moore, only daughter of the society leader whom Trumble has marked as his prey. Mutual attraction follows the meeting, though Jason, while recognizing the fact that Miss Mildred is partial to him, forbears from taking advantage of the situation. On the contrary, the crafty Trumble urges Jason to press his suit, for the master criminal knows that Jason's entree to the Moore home will give him the opportunity for which he is waiting. A week prior to the date of the fancy-dress ball, Jason received a card of invitation. He decides not to avail himself of the invitation. Trumble, in a rage, accuses Jason of ungratefulness. Whereupon Jason relents, and sends his acceptance. That night Trumble plans his coup. Thus Jason will be certain to stroll outside the country house with Mildred Moore. Some pretext will be invented whereby Jason will be called away from her, her abduction will follow, and another young woman, attired in Mildred's costume, or its duplicate, will be substituted in her place. Upon Jason's return, he will conduct his masked partner into the house, where, with the assistance of outside confederates, Mrs. Moore will be enticed upstairs and robbed of her jewels. Everything goes as planned, save that Jason, upon his return to the garden fails to see upon the arm of his partner a certain mole, to which, earlier in the evening he had referred as a "beauty spot." His suspicions aroused, Jason conducts his partner to the house, excuses himself, and loses no time in acquainting the detectives, who are present at Mrs. Moore's request, with his suspicions. The girl is caught, unmasked, given the third degree and forced to confess. A trap is set, and Trumble, with others of his gang, are captured. Jason forces Trumble to tell where Mildred is secreted and then rescues the frightened girl. Having returned the girl to her mother, Jason makes an honest confession, in which he accuses himself as the instrument, though an unwilling one, whereby Trumble was enabled to carry out his scheme. Mildred and her mother forgive him, however, and soon after the engagement of the young couple is announced.