Pledging to revenge the execution of his brother, whom the District Attorney caused to be convicted, Richard Allen, a quaint individual who takes delight in concealing his identity by playing the role of a valet to an extravagant young man in New York, plots for the downfall of the prosecutor and educates his cleverest female crook, “Three-Arm Fanny,” with a view to having her fascinate and marry the District Attorney. The “Master Mind,” under various disguises, informs the District Attorney that he will receive the four aces at certain intervals and when he receives the ace of spades, the end will be near. Richard Allen, known as the “Master Mind,” conceives many diabolical plots looking forward to the ruination of his enemy, the District Attorney, and finally succeeds in arousing his anger and jealousy, and is about to crush the unsuspecting attorney when “Three-Arm Fanny,” who has really fallen in love with her husband, pleads with the “Master Mind” to withdraw and the “Master Mind,” who has come to love Fanny himself, does withdraw through love for her, and disappears, to be seen no more. The powerful gang of crooks, over which he held a formidable leadership, is disbanded and the District Attorney, not knowing that Fanny is a reformed crook, goes on in his own way, becomes governor of the state, and everything ends as it should.