Act 4 begins back at Friar Laurence's cell with Paris telling Friar Laurence about his upcoming marriage to Juliet. Friar Laurence is surprised by this news although he tries not to show it. He knows that Juliet will be upset since he already married her to Romeo, so she is not going to want to marry Paris. At that moment, Juliet walks in and asks if she can speak to Friar Laurence. Paris offers to leave and kisses Juliet goodbye saying he will see her on Thursday for their wedding day. As soon as he exits, Juliet panics and tells Friar Laurence that if he doesn't have a way to prevent this wedding, she will kill herself. Friar Laurence tells her to hold on because he has an idea. Rather than marrying Paris, if she has the courage to fake her own death, he can help her escape. He explains that he has a potion that will slow her breathing and make her turn cold for forty-two hours. During this time her parents will find her and put her in the monument with all their dead relatives. Then Friar Laurence will deliver a note to Romeo telling him about the plan so that Romeo can break Juliet out of the tomb shortly after she wakes up and take her away to Mantua to live with him. Juliet agrees to try it. Friar Laurence reminds her to act pleased about the marriage and ask that she not be disturbed that evening so that she can take the potion without anyone noticing. He says he will send one of the friars to deliver the letter to Romeo in Mantua right away.

     Scene two takes place in the Capulet household where the servants are preparing for the wedding of Juliet and Paris. Juliet enters having returned from what her family assumes was confession. She goes to her father to apologize for her behavior. She says she will do as he wishes her to do. Her father is pleased and asks that Paris be fetched to hear this good news, but Juliet tells him that she ran into Paris at the church and told him as much herself. Capulet instructs the Nurse to go help Juliet prepare. He assures his wife that he will stay up all night if need be to prepare for this wedding tomorrow.

     In scene three Juliet is in her bedroom. She assures the Nurse that she feels ready for the wedding tomorrow. Then she tells her mother that she would like to be left alone overnight to get some sleep. Before Lady Capulet leaves the room, Juliet tells her farewell, for she knows she may never see her again. Then she panics and thinks about calling the Nurse back to her, but she knows she must complete this task alone. Once Juliet is alone, she has a long soliloquy where she outlines all the possibilities of what could happen in the next few days. First, she worries that the potion won't do anything, and she'll have to marry Paris the next day. She looks at her dagger and reassures herself that she will kill herself before she would allow that to happen. Next, she worries that perhaps the potion is actually poison, which Friar Laurence has given her because he realizes he made a mistake in marrying her to Romeo. However, she thinks that he is a godly man, and he would not kill her. Then she considers what would happen if she wakes up in the tomb before Romeo arrives to rescue her. She wonders if she would suffocate from a lack of air. She pictures being surrounded by the bones of her many dead relatives, including Tybalt, who died just recently and won't look or smell very nice. She fears that these sights and smells will drive her insane, and she might pick up a bone and bash in her brains. In her panic, she forces herself to just drink the potion and hope for the best, so she does and collapses onto her bed.

     In scene four the Capulets along with the Nurse and several servants continue to make wedding preparations. Shakespeare liked to intersperse scenes featuring some of the lower class people so that the poorer people who would view the performances could have someone that they could relate to, especially in this play when the majority of the featured characters are lords, ladies, counts, and other high society positions. At the end Capulet instructs the Nurse to go wake Juliet up.

     Scene five is back in Juliet's bedroom where the Nurse comes in and begins opening up the curtains, speaking to Juliet about her big day. Finally, she notices that Juliet is unresponsive, so she goes over and realizes that Juliet is dead. She screams for help, and Lady Capulet arrives first. She is heartbroken that her only child has died. Then Capulet, Friar Laurence, and Paris enter. Friar Laurence feigns ignorance and asks if everything is all set for the ceremony. Capulet explains that Juliet has died. Paris can't believe it. Friar Laurence tries to comfort them all and urges them to hastily hold a funeral. Capulet decides that the things they had planned for the wedding, such as the flowers, food, and musicians, can be used for the funeral instead. Peter delivers the message to the musicians that they will have to change their repertoire from joyous tunes to sad laments.