Friar Lawrences talks to Paris about the marriage of him and Juliet. Juliet does not want to marry him, but it is not her choice. This effects the marriage because Juliet refuses.
Juliet is in deep lament. Paris believes that her grief has made her unbalanced, so he suggest they marry soon so she can stop crying. Her mourning has effected the wedding date.
Juliet threatens to kill herself if she has to marry Paris. When she threatens herself Friar Lawrence helps come up with a plan.
Friar Lawrence comes up with the plan that Juliet must drink a potion the night before the wedding that makes her appear dead. Juliet is scared, and has lots of thoughts in her head about this.
His plan includes the Capulets putting her in her tomb, and the word being spread out to Romeo. Romeo will then come get her when she awakens, and leave without their parents hatred. This is giving Romeo and Juliet a chance to live a happy life.
He then gives her the potion to take. This can affect the wedding, and the rest of Romeo and Juliets love life.