The Question and Answer section for Paper Towns is a great resource to ask questions, find answers, and discuss the novel.
1) Q and Margo’s discover the body of Robert Joyner in the park.
2) Margo goes to Q’s window and wants him to go with her to get revenge on her former boyfriend (he dumped her).
3) Margo disappears.
4) Q looks for clues as to where Margo has...
What chapter are you referring to?
I believe the information you are looking for can be found on page 239 of the text.