The key that drives the plot of the novel is the one that Oskar finds inside the envelope labeled “Black” in the blue vase in Dad’s closet. This key forms the basis for Oskar’s expedition around New York. As Oskar travels around the city, meeting every person with the last name “Black” in alphabetical order by first name, he must overcome several of his fears—traveling across bridges, riding the subway—and learns about others’ lives by pursuing his own quest. Ultimately, what’s behind the lock that the key unlocks isn’t the point; rather, the main function of the key is the personal growth it allows Oskar to achieve, since it gives Oskar a sense of purposefulness in the face of events that seem chaotic and uncontrollable. Other keys also open and close both literal and metaphorical doors in the novel. Grandma has kept Grandpa’s key to the apartment for forty years. She gives it to him when he returns, but Grandpa eventually buries the key in Dad’s coffin, along with all letters to his unborn son. Oskar wears the key from the vase over his heart, tied to his apartment key: his Dad is always the driving force of the quest, but the quest ultimately leads him back to his family. Like Dorothy in the Wizard of Oz, Oskar has had the power to return home all along.