Proteus, a young gentleman of Verona, in love with Julia, is unable to persuade his friend Valentine to stay home rather than depart to the court of Milan for further gentlemanly training. Antonio, ignorant of his son Proteus’s love affair, insists that he further his education and sends him to follow Valentine. Before departing, Proteus exchanges rings and vows of love with Julia.

Valentine arrives in Milan and falls in love with Sylvia, daughter of the duke of Milan. Sylvia returns Valentine’s love, but her father plans for her to marry Turio, a wealthy gentleman also at Milan. Proteus soon arrives, and he too falls madly in love with Sylvia. Unaware of Proteus’s change of heart, Valentine tells him of his plans to elope with Sylvia. Proteus, agonizing over his sudden choice, decides that Sylvia is worth more than Julia or his friend, and he betrays Valentine’s plans to the duke. The duke, enraged, banishes Valentine, and locks Sylvia up. He then engages Proteus to aid Turio in obtaining favor with Sylvia, an opportunity Proteus accepts in order to gain access to Sylvia for himself. The banished Valentine is captured in a forest by outlaws, who make him their chief.

Julia, longing to be reunited with Proteus, arranges to travel to him safely dressed as a man. She arrives in Milan disguised as the page Sebastian, and overhears Proteus wooing Sylvia. Sylvia scorns his attentions, and Proteus then hires “Sebastian” to woo Sylvia for him. Reluctantly, Julia/Sebastian does so, and she/he is relieved to find that Sylvia rejects Proteus’s suit.

Sylvia escapes from Milan and goes in search of Valentine. In the forest, Sylvia is captured by outlaws, and then rescued by Proteus, who takes advantage of the situation to press his attentions on her. Valentine rescues her from Proteus, and condemns his former friend. Proteus, realizing his contemptible actions, repents and is forgiven. “Sebastian” reveals her true self to him, and Proteus, amazed at her dedication, repents his inconstancy and returns to his true love, Julia. In pursuit of Sylvia, the duke arrives, and—seeing Turio act cowardly in the face of Valentine’s chivalry—he accepts Valentine and Sylvia’s betrothal. Proteus and Valentine are reconciled with each other, each with their loves, and all look forward to a future of “mutual happiness.”