history of her own with the building, Mr. Black ends his travels with Oskar, who struggles with his departure. He tries to visit Mr. Black again later but finds out he has moved house, presumably to be with Ruth, and is selling his apartment, leaving behind a card for Oskar, reading "Oskar Schell: Son". Eight months after Oskar initially met Abby, he finds a message from her on the answering machine. Oskar had not touched that phone since his father died because his father's last words had been on an identical answering machine which Oskar had kept hidden from his mother. Oskar finds out that Abby called him directly after his visit, saying she was not completely honest with him and might be able to help. Oskar returns to Abby's apartment after listening to this message, and Abby directs him to her ex-husband, William Black. When Oskar talks to William, he learns that the key once belonged to William's father. In his will, William's father left William a key to a safe-deposit box, but William had already sold the vase at the estate sale to Thomas Schell. Then, Oskar tells William something that he "never told anyone" – the story of the last answering machine message Oskar received from his father, during the attack of 9/11. Disappointed that the key does not belong to him, Oskar then gives William the key and goes home angry and sad, not interested in the contents of the box. Oskar also discovers that his mother knew about his activities the entire time and was contacting everyone with the name Black in New York City. After the first few visits she called every Black that he would meet and informed them that Oskar was going to visit and why. In response, the people Oskar met knew ahead of time why he was coming and usually treated him in a friendly manner. Resolving to try to move on from his father's death, Oskar bonds with Ron after finding out that he met his mother at a support group after having lost his wife and daughter in a car accident. On the second anniversary of his father's death, Oskar meets with "the renter" and they go to dig up his father's grave. Contemplating on what to put into the empty coffin, "the renter" decides to bury various letters that he had written to his unborn son. Shortly