Paris is talking with Father Laurence, to prepare for the wedding on Thursday. Friar Laurence says it's all happening too fast and that he's concerned that Paris doesn't even know if Juliet wants to marry him.
Of course, Friar Laurence does know what Juliet wants. He's lying—trying to affect the world through language without revealing what he knows.
Juliet arrives. Paris greets her as his wife. Paris is loving, but condescending, assuming that she loves him. Juliet is evasive and mocks Paris without his realizing it. Friar Laurence steps in saying it is time for Juliet's confession.
Bland Paris takes love for granted. Juliet masks the meaning of her words with word play.
Once they're alone, Juliet draws a dagger and threatens to kill herself unless the Friar can help her.
Love is here linked to violence, and suicide brought up as a way to escape society.
Friar Laurence quickly comes up with a plan: he gives Juliet a potion that, for forty-two hours, will put her into a sleep so deep it will appear as if she has died. He tells her to agree to marry Paris Thursday, but to take the potion Wednesday night. Instead of a wedding, the Capulets will hold a funeral, and inter Juliet in their family tomb. Meanwhile, the friar will get word to Romeo, who will come to the tomb in time to be there when she wakes, and the two of them will together go to Mantua.
To save her love with Romeo, Juliet must make it look like she killed herself, which foreshadows her actual suicide for love at the play's end. Incidentally, death can be seen as the ultimate night, the ultimate privacy; and it is privacy from the social world that Juliet needs in order to share her love with Romeo in peace.