I understand your confusion, as this book is very intricately-written. It is being told from a hospital in Rutterburg, Vermont. Most of the plot is in the past, mostly in Monument, Massachusetts and on the road to find his father. Also, Adam Farmer's real name is Paul Delmonte. His father was in the witness protection program and the family changed their names. Also, making it even more fun, Paul is delusional and often says things that are not true. (An unreliable narrator)
Chapter 4 is a taped conversation between A. (who you can probably tell is Adam/Paul) and T. (Maybe this stands for "Therapist"?). It takes place in the hospital where Adam/Paul ends up.
The T. asks A. if he wants to talk about Paul Delmonte (himself) or Amy Hertz. Amy was his girlfriend, a rather wild girl who does "numbers" on people--practical jokes that challenge authority. Adam has some issues around his identity, as you could imagine, so he probably has lots to say about "Paul Delmonte" and the witness protection thing.
A. gets another headache (apparently, these are common for him) and the session is ended.
Hope this helps! Hang in there! This book is exciting but very challenging to read.