Quentin is in love with Margo but realizes he can never truly have a life with her.
Q spent his time loving Margo from afar. Until she climbs into his window and asks him to join her on a revenge spree, they end up pranking everyone who did Margo wrong.
Come back with me Margo.
Q does research about what Margo was talking about. "Paper Town" in New York.
When Margo goes missing, the next day, she hasn't left without a trial. Margo leaves little clues to where she will be. Q finds clues and discovers she is on her way to a "Paper Town" in Agloe, New York.
Q finds Margo in an abandoned house. She changed in the days he didn't see her. He asks Margo to go back to Florida with him.
Margo wants to stay in Agloe and offers for Q to stay with her. But he realizes the place he has to be is with his friends and Margo is just a "Paper Girl" in a "Paper Town" and shell be fine.