Pierre Duval, a Frenchman, earns enough to support his son Jacques as an art student in Paris by teaching piano playing. He lives with three cronies in a French boarding house in the New York Latin quarter. The impending war sends Jacques home from Paris, and as he is about to leave Raoul Vaux, a crooked art dealer, induces him to bring some cleverly disguised paintings with him, knowing that the art student's work will be passed at the custom house with but a glance from the customs officers. The secret service suspects Jacques of being Vaux, and Ellen Ingram, a clever girl operative, is put on his trail, and she moves to the same boarding house where Jacques and his father live. The father, proud of his son, tries to keep his financial condition concealed, and secures a position as night watchman in an art gallery. Vaux, who has come to America, plans to steal a picture, and gains admission to the gallery, cuts a fine portrait from its frame and escapes unrecognized. Jacques, hearing that his father is in the art gallery, goes there, but his father sends him home. Later Duval finds the painting missing and notifies the police. He is arrested, but freed. Jacques meets Vaux, who gives him a canvas on which to paint a watercolor. By accident, Jacques finds the stolen painting hidden beneath. While he runs to trap Vaux the police catch Duval looking at the painting and he is arrested. Ellen Ingram, the girl detective, sends operatives to help Jacques and Vaux is captured. The old man, who suspects his son of stealing the painting, pleads guilty himself, and they all go to the police station, where affairs are straightened out, and the old father takes his son into his arms. An affection has sprung up between Jacques and Ellen and they are married, an event made possible by the reward received by Jacques from the French government for the arrest of Vaux.