Valentine and Proteus travelled to Milan, Valentine's father sent him to take a position in the Duke of Milan's court, but proteus did not like leaving his beloved Julia. While in Milan, Valentine falls in love of the Duke's daughter Silvia.  Silvia was betrothed to Thurio, a wealthy courtier, although Silvia prefers Valentine. The two decide to elope, and Valentine confided in Proteus; Proteus, however, is smitten himself by the sight of Silvia. In order to get Valentine out of the way, Proteus betrays the plan to the Duke. Valentine is banished, Silvia is confined to a jail, and Proteus becomes a confidant of the Duke in matters concerning Thurio and Silvia.
Valentine joins a band of outlaws and is elected their leader. As the play progresses, Julia—disguised as a boy page—enters Milan in search of Proteus, who is trying unsuccessfully to woo Silvia on the sly. Silvia, on the other hand, still longs for Valentine, and cares nothing for Proteus or Thurio. Julia, ironically now in service as a page to Proteus, becomes an intermediary between Proteus and Silvia. Silvia finally tires of the situation and escapes Milan in search of Valentine. As fate would have it, Silvia is captured by Valentine's band of outlaws.
Unfortunately, the Duke learned of Silvia's escape, and he, Proteus, and Thurio all set off to rescue her. Proteus recovers Silvia before the outlaws can bring her to Valentine. Valentine encounters them as Proteus makes the case for his love to Silvia; the two confront and eventually make peace with each other. In a gesture of reconciliation, Valentine even offers Silvia to Proteus, which causes Julia  to faint,  Proteus recognizes her, much to his shame. The Duke and Thurio arrive upon the scene, but Thurio backs off his claim to Silvia when challenged by Valentine. As the play ends, Valentine gets Silvia with the Duke's approval, Proteus and Julia are reconciled, and the Duke grants a pardon to the band of outlaws