This infamous line appears in Act 3, Scene 1, of the play, following a heated exchange between Mercutio and Tybalt, a Capulet kinsman. After Tybalt challenges Romeo to a fight, Mercutio steps in to defend his friend and engages in the duel instead. During the fight, Mercutio is mortally wounded by Tybalt.
As he lies dying, Mercutio curses both the Montague and Capulet families, wishing a plague upon them for their senseless hatred and rivalry. The phrase "A plague on both your houses" carries a deeper meaning that reflects the destructive consequences of such feuds, which ultimately lead to unnecessary violence and the tragic deaths of innocent individuals like himself.
Mercutio's lament underscores the devastating impact of the long-standing conflict between the two families, and serves as a poignant reminder of the futility and absurdity of their quarrel.
The phrase has become emblematic of the destructive nature of feuds and conflicts, resonating with audiences far beyond its original context in Shakespeare's play.