Arthur Von Bauer's desire to forget the death of his mother and father, brings him to New York, where he secures a position at the Garden Cabaret. Arthur's inheritance of musical genius from his father makes him a popular musician. A panic on the Stock Exchange ruins Donald Ober overnight and rather than face the ruin he commits suicide, leaving the care of his invalid wife to Mignon, their daughter, whose greatest accomplishment is a wonderfully cultivated voice. Their home is sold over their heads, and Mignon realizes she must do something to provide for her mother and self and finds employment singing at the Garden Cabaret. Arthur is working on an expression of his loneliness which he puts into music and calls it "The Song of the Heart." On the other side of the wall in the next building, Stephen Richards, a degenerate and piano player, in a low dive, hears and steals Arthur's composition and has it copyrighted under the title of "A Tuneful Melody." Mignon. who has taken rooms above, also hears the song and is charmed by it. After a few days at the Garden Cabaret, the proprietor, McChesney, sees in Mignon a different sort of girl as usually inhabits his place, and he makes plans to take advantage of her, which plan is frustrated by Arthur at the cost of his and her positions. He then composes a light operetta in which is incorporated "The Song of the Heart," in which Mignon sings the leading role and makes a greater hit than the opera itself. Richards, having stolen the melody, comes forward, claims authorship, and proves by copyright his claim. Arthur loses his position. Mignon makes every endeavor to prove him innocent even to the extent of visiting the dive to plead with Richards. A few nights later a scuffle at a card table near the piano being played by Richards, a stray shot finds its way to the piano player's back. He is taken away to the hospital where he is told that he cannot live. He confesses to having stolen "The Song of the Heart," and Arthur is restored to his position, and his reward is Mignon.