When his master Valentine questions him how he could possibly know that Valentine is in love (and with Madam Silvia), Speed refers to the state of Valentine’s friend Proteus when they last saw him in Verona and how Valentine is currently a mirror reflection of his friend. Indeed, like Proteus, Valentine is now careless of dress, inclined to sing love songs like a robin, and is wont to sigh, complain, and weep while isolating himself from company. Valentine is reluctant to believe that all those qualities are readily apparent in him, but Speed assures him that they are indeed. Subsequently, arguing that Silvia’s beauty is beyond compare, Valentine tries to justify his lovesickness when Silvia appears to ascertain the quality of the letter that she had commissioned Valentine to write in praise of her friend. The letter is good, and Silvia is satisfied when Valentine apologizes for not having written the letter as well as he could, which he would have if he only knew for whom the letter was intended, he assures her. The disclaimer flusters Silvia who returns the letter, arguing that she would not keep a letter which has been written unwillingly. Valentine urges Silvia to keep the letter, admitting that it was written with her in mind. Moreover, Valentine promises to write her a letter that is even better than the one already written. Inexplicably, Silvia tells Valentine to go ahead and write a better letter but to keep it for himself. She leaves, delighting Speed. When asked what he finds so amusing, Speed replies that Madam Silvia is writing a love letter to Valentine by having Valentine write it himself. Valentine isn’t amused, however, and refuses to have anything to do with supper which Speed is eager for them to partake of.
On the verge of leaving Verona, Proteus has parting words with Julia. He promises her that he’ll return the first chance that he gets. When she replies his return will be the sooner if his love for her remains undiminished, Proteus invokes the fates to malign him with a calamity the moment his feelings for Julia diminish. They exchange tokens of their love, including a kiss, before parting. Presently, Proteus’ father’s servant Panthino arrives to urge Proteus to prepare for his departure. Proteus sadly obliges.
As Proteus’ servant Launce and his dog Crab prepare to accompany Proteus, who is due to sail to the Emperor’s court, Launce goes to such lengths to chide his dog Crab, for failing to shed one tear in parting with Launce’s family, that Panthino, in turn, chides Launce for failing to expeditiously embark. Launce attributes his delay to Crab’s ingratitude, but Panthino will have none of his clowning and exhorts Launce to make haste. Launce obliges, all the while clownishly arguing that even if the tide lowers and the opportunity to sail is lost because of his—Launce’s—delay the volume of his tears at parting will make up for the lowered tide.
When Valentine confirms that he is in fact sad as Silvia notes him to be, Sir Thurio, Valentine’s rival to Silvia’s love, takes exception and argues that Valentine is dissembling. Consequently, the two rivals engage in verbal sparring, compelling Silvia to act as mediator. Presently, Silvia’s father the Duke of Milan appears to apprise Valentine of happy news: his friend and boyhood companion Proteus is on his way to Milan. Valentine is indeed gladdened, and he praises Proteus’ worth as far exceeding his—Valentine’s, suggesting that the service Proteus will render the royal court will exceed Valentine’s. Informing Valentine that he’ll have Proteus join him right away, the Duke leaves with Thurio in tow. Meanwhile Valentine and Silvia fall into a dispute about the nature of love when Proteus appears. Greetings are exchanged and upon Valentine’s insistence, Silvia agrees to take Proteus into her service while Proteus assures her he’ll serve her faithfully. By and by, Thurio arrives to inform Silvia that her father requires her presence. When Thurio and Silvia leave, Valentine tells Proteus of life’s irony; of how he—Valentine—had chided Proteus for being slave to love only to become a slave to love himself on account of Silvia. Valentine proceeds to praise Silvia with hyperboles at Julia’s expense, compelling Proteus to chide Valentine. Valentine is irrepressible, however, as he tells Proteus that he and Silvia are so in love with another that they have decided to elope, defying Silvia’s father who, on account of Thurio’s wealth, is partial to having his daughter marry Thurio. Presently, having promised to join Valentine in his quarters, Proteus reflects on his precarious state of mind. He realizes that he has fallen in love with Silvia. Proteus resolves to restrain himself from wooing Silvia if he can, but if he can’t then too woo her with all that he’s got.
When Valentine’s servant Speed welcomes Proteus’ servant Launce to Milan, Launce makes it be known that a welcome doesn’t mean much unless the one being welcomed is treated to drinks in an alehouse. Speed assures Launce that he will be treated to drinks by and by. For now, Speed questions Launce about his master Proteus and Julia: Will they marry? In the most roundabout manner, typical of his clownish ways, Launce replies that he doesn’t know, and when asked what he thinks about the fact that Speed’s master Valentine is head over heels in love, like Proteus, Launce replies that he doesn’t care and only repeats his wish to be treated to drinks at an alehouse. Speed obliges him.
Alone, Proteus agonizes over his predicament. If he pursues Silvia’s love, he will betray and lose Julia and Valentine. If he’s faithful to Julia and Valentine, he will be false to himself. Cursing Love which is compelling him simultaneously to make a vow and then break it, Proteus decides to inform the Duke of Valentine’s secret plan. With Valentine disgraced and out of the picture, Proteus is certain that he can undermine Thurio and win Silvia’s love for himself.
Having resolved to join Proteus in Milan, Julia asks Lucetta how the undertaking might be best put into motion. However, arguing that the journey is too hard and that Julia’s passion may end up consuming her, Lucetta tries to dissuade Julia. Julia remains fixed to her intention, however, as she argues that inertia will be the cause of her being consumed by her passion as her passion’s confinement will cause it to metastasize. Reluctantly, expressing her skepticism if Proteus will prove worthy of her dedication, Lucetta agrees to look after Julia’s affairs in Julia’s absence.