John Burkett Ryder is a master of finance with a boundless desire for wealth. No mean avarice, but a love of the power to be gained through riches, a domineering will and an unscrupulous soul. Previous to the opening of the story Ryder has compassed the financial ruin and professional disgrace of Judge Rossmore, of the Supreme Court, to avenge himself for certain adverse decisions which the judge has rendered against the corporation. Shirley Rossmore, the judge's daughter, and young Jefferson Ryder returning from Europe on the same boat, have met and register a pretty story interest in each other, being at the time entirely ignorant of the friction now existing between their respected fathers. Shirley has written a novel, and from Jefferson's description of his father has made the star character of the story a fair prototype of the master of finance. Ryder, without consulting his son's wishes, has already announced an engagement between Jefferson and the daughter of Senator Roberts. Shirley Rossmore's book which is written under the pseudonym of Sarah Green gets into Ryder's house and makes such an impression that the great financier employs a detective to find the author. Sarah Green is found and Ryder employs her to compile his biography, not dreaming that she is the daughter of the judge he has ruined. Now comes the battle between the Lion and the Mouse. The Mouse wins the Lion's admiration by the outspoken audacity of her opinion of his life and moral code. Kate Roberts, whom Ryder had selected to be his son's fiancée, elopes with his aristocratic private secretary, "Fourth groom of the bed chamber to the second Prince of England." Ryder, to pacify his son and to offset his attachment for Shirley Rossmore, suggests that he marry Sarah Green, "who has proved herself far more brilliant than the judge's girl." It is then Shirley's turn; she declares her identity and admits that she has secured certain letters from Ryder's desk that will prove her father's innocence. Ryder orders her from the house, then he sits up all night, consumes innumerable black cigars and finally conquers his own vanity. Next day Jefferson Ryder proposes, but Shirley declares that she will never marry a man that has such a father. With bitter words, Jefferson denounces his father; he tells him that the girl he loves objects to the family. But John Burkett Ryder eats a big slice of humble pie; he announces that he will prevent the impeachment of Judge Rossmore and implores Shirley to accept his son. The Mouse has conquered the Lion.