Act IV Scene II
The act starts off with some comic relief, where Lord Capulet is talking with the serving men. Juliet enters, with news after visiting Friar, to tell her father that she will marry Paris. Juliet's plan was to wait until Wednesday night, and before she would go to sleep, take a potion that would essentially render her dead until Friday.
Juliet tells her father that she will marry Paris, and she begs her father for forgiveness--implying to Capulet for disobeying him, but to the audience it is known that she asks just for him not to be mad at her-- and he agrees to forgive her. Capulet, however, is so excited that he moves the wedding up to Wednesday, causing the plan to go wrong, as Juliet could wake up a day early.
Juliet tries to keep the wedding on for Thursday, but due to Capulet stubbornness, it is moved to Wednesday.