William Baldwin, ruined in business by his partner, John Blaisdell, implores Blaisdell's aid, and receives in answer a five-dollar bill across the face of which is written, "Spend this for a gun and use it on yourself." Hopelessly, Baldwin and his daughter, Nan, go to the Yukon, where the father soon dies, and the daughter earns a living in a rough dance-hall, where as "Nightingale Nan" she is the idol of the miners. When Nan discovers that the little claim on Bear creek, the only thing her father has left her, is worthless, she at first collapses. Then she becomes defiant, and tells the miners who have been forcing their attentions upon her that they may have her, the lucky man to be the winner in a card-game, she to take the money won in the game and go away to seek fame and fortune. A bearded stranger wins the game with a pair of deuces, pays her $1,000 a card, and she leaves with him for her cabin. Once there, however, she repents her rash bargain, and implores him to release her, offering the money in return. He makes her sign an I.O.U. for herself, promising to pay the debt at any time in the future that he may see fit. "You'll win success," the stranger tells her, "but in the hour of your greatest triumph I shall claim you, and you must return." She leaves on this condition. Nan's voice wins success for her all over the world. As Mlle. Nanon Boldini five years later she is the reigning operatic queen at La Scala, Milan, and then comes to the Metropolitan opera house. New York, to make her American debut in "Lucia di Lammermoor." Her success is instantaneous. Two of the most important patrons of the opera house, John Blaisdell and James Van Brunt, business rivals, are united in their admiration of Mlle. Boldini, and obtain an introduction. When Nan discovers the identity of Blaisdell, the man who ruined her father, she says nothing, but quietly plans his downfall. She encourages his attention, even at the risk of displeasing a young stranger with whom she has fallen in love. She refuses an offer of marriage from the man who has won her heart, telling him of her promise made under amazing conditions to a man in Alaska five years ago. That promise, she tells him, must be fulfilled, no matter how great the sacrifice she makes in doing so. Inviting Blaisdell to her apartment to dinner, she has a telephone connection so arranged that James Van Brunt, at his downtown office with the receiver at his ear, hears Blaisdell's answers to the carefully prepared questions Nan asks, betraying all his business secrets. As Blaisdell falls across the table in a drunken stupor, after having told everything, Nan's triumph is complete. It is at this moment that two fateful cards, the deuces with which the Alaskan won his game, are thrust under the door, and Nan falls fainting. Next day she prepares for her journey to the northland, ready to pay the price of her five years' freedom. The man she loves insists on accompanying her. Going to her little cabin, she finds it sumptuously furnished. As she turns to her lover in surprise, he places on the table a crumpled "I.O.U." then tears it in two, giving her the pieces. As the realization slowly dawns on Nan that the man she has learned to love is the bearded stranger of so long ago, she fits the two pieces of the "I.O.U." together again, and presenting them to him, creeps into the arms of her stranger-lover.