A composer finds inspiration in his wife's romantic cousin.

After young composer Lewis Dodd's latest symphony is badly received in London, he seeks solace at the Swiss home of his old friend and fellow musician, Albert Sanger. Lewis' arrival causes great excitement among Sanger's four daughters: Kate, Toni, Tessa and Paula. Despite the fact that she is only a teenager, Tessa is in love with Lewis and dreams of helping him to reach his full promise as a composer. The ailing Sanger has reared his daughters away from the conventions of society and now worries about their future. He asks Lewis to contact Charles Creighton, Tessa and Paula's wealthy uncle, if he dies. Finished with family business, Sanger then chastises Lewis for the lack of feeling in his music. When the girls play a little song that Lewis wrote for them, Sanger tells Lewis that, far from being a trifle, the beautiful melody is better than his more intellectual work. Some time later, Sanger dies. Kate travels to Milan to study music, and Toni marries wealthy Fritz Bercovy. Complying with Sanger's wishes, Lewis sends for Creighton, who arrives with his beautiful daughter Florence. Lewis and Florence fall immediately in love, and when they announce their engagement, Tessa, who has a bad heart, faints. Creighton arranges for Tessa and Paula to attend school in England, and Lewis and Florence marry. Six months later, Lewis is frustrated by Florence's efforts to manage his career and the couple quarrel frequently and publicly. When Tessa and Paula run away from their school, Lewis immediately leaves to look for them, ignoring the party that Florence has planned to introduce him to her friends. Lewis fails to find the sisters, but when he returns home, they are waiting. Paula leaves to join Fritz and Toni, who is pregnant, and Tessa stays with Florence and Lewis. When Tessa hears Lewis' latest composition, based on the song that he wrote for her and her sisters, she is disappointed. The next day, Tessa encourages Lewis to put sentiment back into his music. Enthusiastic for the first time since his marriage, Lewis changes his composition with Tessa's help. Florence realizes that Tessa is her rival, despite her youth, and jealously tries to get rid of her, but Lewis comes to her defense. The night of the first performance of Lewis' new work, Lewis finally realizes that he returns Tessa's love and asks her to go away with him, but Tessa refuses because he is married to her cousin. The excitement of Lewis' proposal and the premiere of his composition causes Tessa to have another fainting spell, and Florence insists that Tessa stay home, rather than attend the concert. Lewis' new work is favorably received, but Lewis returns to Tessa before the end of the concert. Florence follows him to tell him that the music has made her understand how much he loves Tessa and so she will not stand in his way if he wants to leave her. Her release is too late, however, as all the conflict has been too much for Tessa's frail heart and she has died.