We meet our hero, Romeo, after a duel between the servants of two enemy families of Verona: the Montagues and the Capulets. Romeo Montague is pining away for Rosaline, a girl we never see. Juliet Capulet, age thirteen, has just heard that Paris, Verona's attractive young bachelor, would like to marry her. The two will meet that night at a masquerade ball at the Capulets' house. Romeo and his friends have decided to crash the Capulet ball – in costume – because Rosaline is on the guest list. Romeo meets Juliet there instead, and they fall madly in love. Afterwards, they discover they are members of rival families, but they are still in love. Romeo stays after the party under Juliet's balcony, and the two use this romantic meeting to plan their marriage. Hasty, but genuine.
This is where things get sticky. Romeo meets with Friar Laurence to arrange the marriage, and Juliet confides in her nurse, who has basically raised her, to act on her behalf and meet Romeo. The Nurse meets Romeo and his friend Mercutio (who thinks the whole situation is hilarious). Romeo tells her to get Juliet to Friar Laurence's, where the two will be married.
Meanwhile, Benvolio, another member of the Montague posse, runs into Tybalt Capulet, who is angry about the Montagues crashing his family party the other night. Romeo, freshly married, strolls into the middle of a tense situation, and as things escalate, Tybalt kills Mercutio. Stricken by grief, Romeo promptly challenges Tybalt to a duel and kills him. Romeo runs away before all of Verona shows up. The Prince of Verona rules that Romeo won't be killed, but banished from Verona. This all puts a damper on the new marriage.
Juliet hears from the Nurse that her new husband has murdered her cousin. She is doubly sad about the death and murder. Mostly Juliet just wants to see her banished husband. The Nurse finds Romeo hiding at Friar Laurence's, and the Friar hatches a plan. Romeo can spend his wedding night with Juliet, but then he must run away, while the Friar finds some way to get the Prince of Verona to pardon Romeo. The marriage will be made public upon his return.
Meanwhile, back at the Capulet house, Paris is working even harder to wed Juliet, who is stricken by grief. Lord Capulet decides a wedding (to Paris) is just the thing to distract her, as he does not know she's already a bride. Juliet spends her wedding night with Romeo, and as he leaves in the morning, she finds out she is to be married to Paris in two days. She refuses and has a violent fight with her parents. Even her nurse thinks she should marry Paris, since Romeo is "as good as dead" to her.
Juliet, trying to figure out what to do, runs over to Friar Laurence's, where she has a weird kiss with Paris. After Paris leaves, she threatens to kill herself. The Friar adds another bit to his plan, and gives her an herbal concoction that will make her appear to be dead for 42 hours. Yes, exactly 42. She goes home, agrees to marry Paris, and takes the poison with the intention of looking dead on the morning of her wedding and being taken to the Capulet tomb where Romeo can find her and everyone can live happily ever after.
Sadly, Romeo is hiding in Mantua, out of the loop, and the news of Juliet's "death" makes it to Romeo before word of the Friar's plan. He buys some poison so he can go to Juliet's grave and kill himself. At her grave, he finds Paris, whom he murders, and then breaks into Juliet's tomb, where he spends some time with Juliet's "dead" body.
He drinks the poison and dies just in time for Juliet to wake up and find him dead. The Friar, who apparently shows up at some point, also finds Romeo dead, and tries to convince Juliet to run away. She refuses (she's been doing a lot of that lately) and kisses Romeo (a lot of that, too) to find that his lips are still warm – she just missed him. He doesn't have enough poison on his lips to kill her, too, so she takes her own life with a dagger. Capulets, Montagues, and the Prince of Verona show up to the tomb and find the dead lovers. Friar Laurence is dragged in to confess everything. The two lords of the rival houses are moved by their dead children's love story and agree to end the feud.