Bertram, the Count of Rousillon, is called to the court to serve the king of France, who is ill of a disease that all the royal physicians have failed to cure. In the entire country the only doctor who might have cured the king is now dead. On his deathbed he bequeaths to his daughter Helena his books and papers describing cures for all common and rare diseases, among them the one suffered by the king.
Helena is now the ward of the Countess of Rousillon, who thinks of her as a daughter. Helena loves young Count Bertram and wants him for a husband, not a brother. Bertram considers Helena only slightly above a servant, however, and will not consider her for a wife. Through her knowledge of the king’s illness, Helena at last hits upon a plot to gain the spoiled young man for her mate, in such fashion as to leave him no choice in the decision. She journeys to the court and, offering her life as forfeit if she fails, gains the king’s consent to try her father’s cure on him. If she wins, the young lord of her choice is to be given to her in marriage.
Her sincerity wins the king’s confidence. She cures him by means of her father’s prescription and, as her boon, asks for Bertram for her husband. The young man protests to the king, but the ruler keeps his promise, not only because he gave his word but also because Helena won him over completely.
When the king orders the marriage to be performed at once, Bertram, although bowing to the king’s will, will not have Helena for a wife in any but a legal way. Pleading the excuse of urgent business elsewhere, he deserts her after the ceremony and sends messages to her and to his mother saying he will never belong to a wife forced upon him. He tells Helena that she will not really be his wife until she wears on her finger a ring he now wears on his and carries in her body a child that is his. He then states that these two things will never come to pass, for he will never see Helena again. He is encouraged in his hatred for Helena by his follower, Parolles, a scoundrel and a coward who will as soon betray one person as another. Helena reproaches him for his vulgar ways, and he wants vengeance on her.
Helena returns to the Countess of Rousillon, as Bertram commands. The countess hears of her son’s actions with horror, and when she reads the letter he writes her, restating his hatred for Helena, she disowns her son, for she loves Helena like her own child. When Helena learns that Bertram says he would never return to France until he no longer has a wife there, she sadly decides to leave the home of her benefactress. Loving Bertram, she vows that she will not keep him from his home.
Disguising herself as a religious pilgrim, Helena follows Bertram to Italy, where he goes to fight for the duke of Florence. While lodging with a widow and her daughter, a beautiful young girl named Diana, Helena learns that Bertram seduced a number of young Florentine girls. Lately he turned his attentions to Diana, but she, a pure and virtuous girl, will not accept his attentions. Then Helena tells the widow and Diana that she is Bertram’s wife, and by bribery and a show of friendliness she persuades them to join her in a plot against Bertram. Diana listens again to his vows of love for her and agrees to let him come to her rooms, provided he first gives her a ring from his finger to prove the constancy of his love. Bertram, overcome with passion, gives her the ring, and that night, as he keeps the appointment in her room, the girl he thinks is Diana slips a ring on his finger as they lie in bed together.
News came to the countess in France and to Bertram in Italy that Helena died of grief and love for Bertram. Bertram returns to France to face his mother’s and the king’s displeasure, but first he discovers that Parolles is the knave everyone else knows him to be. When Bertram holds him up to public ridicule, Parolles vows he will take revenge on his former benefactor.
When the king visits the Countess of Rousillon, she begs him to restore her son to favor. Bertram protests that he really loves Helena, though he did not recognize that love until after he lost her forever through death. His humility so pleases the king that his confession of love, coupled with his exploits in the Italian wars, wins him a royal pardon for his offense against his wife. Then the king, about to betroth him to another wife, the lovely and wealthy daughter of a favorite lord, notices the ring Bertram is wearing. It is the ring given to him the night he went to Diana’s rooms; the king in turn recognizes it as a jewel he gave to Helena. Bertram pretends that it was thrown to him in Florence by a high-born lady who loved him. He says that he told the lady he was not free to wed, but that she refused to take back her gift.
At that moment, Diana appears as a petitioner to the king and demands that Bertram fulfill his pledge to recognize her as his wife. When Bertram pretends that she is no more than a prostitute he visited, she produces the ring he gave her. That ring convinces everyone present, especially his mother, that Diana is really Bertram’s wife. Parolles adds to the evidence against Bertram by testifying that he heard his former master promise to marry the girl. Bertram persists in his denials. Diana then asks for the ring she gave him, the ring which the king thinks to be Helena’s. The king asks Diana where she got the ring. When she refuses to tell on penalty of her life, he orders her taken to prison. Diana then declares that she will send for her bail. Her bail is Helena, now carrying Bertram’s child within her, for it was she, of course, who received him in Diana’s rooms that fateful night. To her Diana gave the ring. The two requirements for becoming his real wife being now fulfilled, Bertram promises to love Helena as a true and faithful husband. Diana receives from the king a promise to give her any young man of her choice for her husband, the king to provide the dowry. Thus the bitter events of the past make sweeter the happiness of all.