1.1: Proteus says an emotional goodbye to Valentine and explains why he's staying behind in Verona while his buddy goes off to see the world – Proteus is in love with Julia and can't stand to be away from her. Proteus then asks Speed if his love letter was delivered to Julia.
2.2: The next time we see Proteus, he's saying an emotional goodbye to Julia. (Proteus's dad has decided to send him to Milan, where Valentine is.) Proteus exchanges rings with Julia and promises to be faithful.
2.4: Proteus arrives at the Duke's court in Milan, greets his best bud, takes one look at Silvia, and then falls in love with his best friend's girlfriend. Left alone on stage, Proteus tells us he's fallen out of love with Julia and his BFF, Valentine. He'll try to stop himself from being in love with Silvia, but, if he can't, he'll do anything he can to win her.
2.6: Proteus gives us a big speech about how he's torn between Valentine and Silvia. Then he announces he's going to get his friend out of the picture by telling Silvia's dad that Valentine plans to elope with his daughter.
3.1: Proteus makes good on his promise and tattles on Valentine so he'll get booted out of the court. After Valentine gets banished, Proteus pretends to be a loving and concerned friend and then escorts Valentine to the city limits.
3.2: With Valentine out of the way, Proteus now schemes to win Silvia's heart and get Thurio out of the way. Proteus comes up with the idea to talk trash about Valentine to Silvia.
4.2: Proteus pretends to be Thurio's friend and acts like he's going to help him get Silvia. They go to Julia's window and serenade her. When Thurio goes home, Proteus makes his move and gets rejected by Silvia.
4.4: Some time between Act 4, Scene 2 and Act 4, Scene 4, Proteus sends Lance to give Silvia a gift – a little lap dog. Here, Proteus learns that his gift never made it to Silvia (the little dog ran away). Proteus meets "Sebastian," who is really Julia. (She's come to see Proteus.) Proteus hires "Sebastian" and then sends "him" to deliver a ring to Silvia (the same ring Julia gave him!).
5.2: Proteus continues to pretend he's helping Thurio get Silvia and gives Thurio some bad advice. When the Duke arrives with news that he's going to the forest to find a runaway Silvia, Proteus announces he's going, too.
5.4: In the forest, Proteus has somehow caught up with Silvia. He tries, unsuccessfully, to convince her that she owes him for finding her. When Silvia tells him to scram, Proteus tries to rape her. Proteus is confronted by Valentine and apologizes for being a disloyal friend (he doesn't apologize for trying to assault Silvia). When Valentine offers to let Proteus have Silvia for himself, he doesn't have a chance to reply because "Sebastian" faints and then reveals that "he" is actually "Julia." Seeing Julia, Proteus falls back in love with her and gets engaged.