When Romeo hears of Juliet's death from Balthasar, he reacts impulsively to the news, shouting, "I defy you, stars!" (V.i). He means to counteract fate by taking his own life. Romeo first asks Balthasar if the Friar has sent a letter and then he begs Balthasar to acquire some fast horses. He remembers a poor apothecary in Mantua and buys poison from him, even though it is against the law in town to sell poison. Romeo tempts the poor apothecary with gold to convince him to sell the poison. Romeo intends to travel to Juliet's tomb and die by her side, so they can be together in death.
Romeo mistakenly learns that Juliet is dead in Act Five, Scene One. After Romeo is banished from Verona for killing Tybalt, Juliet and Friar Laurence devise a plan to reunite the two lovers: Juliet will fake her own death, and her body will be brought to the Capulet crypt, where she will meet up with Romeo. The news of this plan is to be delivered to Romeo by a messenger, Friar John; however, due to an outbreak of illness that leaves him quarantined, Friar John is delayed and is unable to deliver the message.
Thus, Romeo receives news of Juliet's death from Balthasar, "Romeo's Man," who believes (like the rest of Verona) that Juliet has actually died. Upon receiving this news, Romeo vows that he "will lie with thee [Juliet] tonight." He rushes to an apothecary and buys a dram of poison for forty ducats. After traveling back to Verona and sneaking into the Capulet's crypt, he kills Paris (who had been hovering outside the tomb) and commits suicide by drinking the poison. Due to this tragic error in communication, Romeo dies at the side of his merely sleeping (not dead!) beloved.