Oskar’s quest for the lock ends with no answers about his dad, demonstrating the inevitability of ambiguity. Oskar cannot gain any answers about his dad from William, who never really knew Oskar’s dad and had a difficult relationship with his own father. Beyond the safety deposit key, William’s father didn’t offer him anything personal to remember him by, leaving William feeling forever alienated from his father. Although William will finally get to learn what his dad left him in the safety deposit box, he will never get what he actually wanted from his father in the form of loving, heartfelt communication. Therefore, the quest has led Oskar to another father-son relationship trapped in limbo. Oskar expresses his need for concrete answers by confessing to William his secret about the phone and his guilt and asking for forgiveness. Although, as an outsider, William cannot possibly give Oskar the forgiveness he seeks, because Oskar had hoped this quest would bring him answers, William, as the endpoint of his quest, becomes the closest Oskar can have to closure.

The letter from Stephen Hawking at the end of the chapter counterbalances Oskar’s disappointment by highlighting the importance of the ambiguity he must live with. Stephen Hawking represents Oskar’s love of science and the way physics categorizes, organizes, and explains the universe. Physics also has a deep tie to math, which often has concrete correct answers. However, Stephen Hawking expresses a desire to be a poet, which is tied to literature, the humanities, and ambiguity. Hawking even explicitly says that life depends on not knowing. This sentiment echoes the lessons Oskar’s dad taught him in the last Reconnaissance Expedition and the Sixth Borough fable about how not having a concrete answer can also lead to exploration and imagination. If, as Stephen Hawking suggests, so much of the universe depends on dark matter, something no one can see or understand, then inventing and imagining things about that unknown is not only an inevitable part of life but a necessary and beautiful one.