Oskar gets let out of school early because of 9/11.
Oskar visits an expert on key's and figures out to key is used to open a lock. Oskar comes up with a plan to find the owner of the key. He decides to visit every single person in New York that has the last name "Black"
Oskar travels to Abby Black's house to find out more information on the key. She sends Oskar to her ex-husbands office.
The renter returns home after digging up the coffin, the grandma was asking him things. He told grandma the truth that he was out with Oskar, breaking their promise. He sold his apartment and moved to the airport.
Oskar looks at a book that his dad created and looking at the book gives him strength to keep moving forward.