Peter Van Houten comes back to America to attend Augustus Waters' funeral. Unbeknownst to Hazel, Augustus had remained in contact with Van Houten after their first disastrous meeting in Amsterdam. Augustus had continued writing him and had made an impression on Van Houten, so much so that he decided to attend Augustus' funeral and attempt to reconnect with Hazel.
When he first approaches her after the service, she is completely disgusted with him, especially after he explains that the letters Augustus had written to him demanded answers to Hazel's questions about the open ending to his novel. Van Houten, in his typical drunk fashion, angers Hazel with his nonsensical, lofty answers that she believes are not really true answers at all. She feels really insulted and demands that he leave.
Ultimately, Van Houten tries to explain himself to Hazel one last time before he leaves to return to Amsterdam. During this meeting, Van Houten reveals that Augustus had sent him a copy of a eulogy that he had written for Hazel; he sought Van Houten's help in improving his writing. Van Houten also softens up and reveals true insight into his novel at last, particularly the truth that he based the story on his daughter Anna who died at only eight years old.
Peter Van Houten comes back to America for Augustus's funeral. Even after their disastrous meeting, he still remained int contact with him (we learn later that it was request for an epilogue for An Imperial Affliction). He comes to apologize to Hazel, for his terrible attitude toward her in Afghanistan
Peter Van Houten returns to America after finding out that Augustus had died. He came for the funeral. They had met in Amsterdam but the meeting did not go very well. They came in contact after Augustus had asked for an epilogue for An Imperial Affliction, a book that both Augustus and Hazel loved very much. Van Houten tries to explain himself to Hazel, and later explains how the book was written about his actual daughter.