Mercutio's quote "a plague o'er both your houses" predicts future events in several ways. For one thing, it highlights the consequences of the feuding. Of course, Mercutio probably wasn't the first and will not be the last to die because of the bitter tension between the two families. Mercutio's quote foreshadows a continuing of aggressions. While he doesn't know that Romeo has a reason to stop the fighting, he sees the high price of the feuding. Eventually, Romeo will kill Tybalt and bring about his own exile. The death of Mercutio marks the downturn of Romeo and Juliet. In the end, the plague of hatred destroys both houses and "heaven finds means to kill your joys with love...all are punish'd."