Mercutio is Romeo's friend and kinsman of Prince Escalus, and the play does not place him in either of the two rival houses. He is the most mocking voice of the group, and he dies in Act III, scene 1, wounded by Tybalt in a duel that Romeo had refused, after cursing both families.
In Act I, scene 4, on the way to the ball, he tries to pull Romeo out of his sadness with mockery and describes Queen Mab, the midwife of the fairies who visits the dreams of each person: the lover dreams of love, the lawyer of fees, the soldier of cutting the throats of foreigners. Romeo interrupts him, saying he speaks of nothing. In Act II, scene 4, he describes Tybalt, who sent a challenge to Romeo's house, as the captain of courtesies, who fights as if he were singing, keeping time; and when Romeo again trades puns with him, he salutes him: now, at last, he is Romeo.
In Act III, scene 1, Tybalt calls Romeo a villain, and Romeo refuses the duel. Mercutio calls the refusal "calm, dishonorable, vile submission" and draws his sword in his place. Romeo tries to part the two, and Mercutio is wounded under his arm. He says it is a scratch, that tomorrow they will find him a grave man, and repeats the curse: "a plague on both your houses."
He dies offstage, and Benvolio brings the news to Romeo, who kills Tybalt and is banished. At the end of the play, the Prince says that he has lost two kinsmen, Mercutio and Paris (Act V, scene 3).