1.1: Benvolio tries to stop a fight in the streets, but ends up taking part in it. Afterwards, he talks to Romeo's parents, and promises to find out why Romeo has been acting depressed. He meets up with Romeo, who tells him the problem is that he's in love with a girl who isn't interested in him.
1.2: In hopes of helping Romeo get over Rosaline, (the recipient of Romeo's unrequited love), Benvolio convinces Romeo to crash the Capulet party. They'll compare Rosaline to the other women there and will see that she's not all that.
1.4: He chills with Romeo and Mercutio
1.5: Benvolio has fun at the Capulet party, then tries to drag Romeo away once it's clear that the party's breaking up. Romeo, smitten with Juliet, refuses to leave.
2.1: Benvolio and Mercutio try to figure out where Romeo disappeared to. They soon give up and head home.
2.4: The next day Benvolio and Mercutio still don't know where Romeo is. They know that Tybalt has challenged their friend to a duel. Benvolio says he is sure Romeo will uphold his honor and fight Tybalt. When the Nurse shows up, Benvolio joins Romeo and Mercutio in the general mockery of this poor woman.
3.1: As usual, Benvolio tries to avoid fighting with the Capulets, but gets drawn in anyway. When Tybalt strolls in, Benvolio tries to get everybody to calm down. He tells Mercutio and Tybalt either to chill or to continue their argument in private. As usual, nobody listens. Benvolio witnesses Tybalt and Mercutio's duel, and he is with Mercutio when he dies. Then he watches Romeo and Tybalt fight. When Tybalt dies, Benvolio tells Romeo he has to run away or the Prince will put him to death. When the Prince arrives at the scene of the slaughter, Benvolio explains what has happened.