What drives Oskar?

When Oskar discovers a strange key hidden in his late Dad's closet, he begins a quest to visit everyone in the New York City phonebook surnamed Black (472 names), most of the time accompanied by an aged upstairs neighbor, a long-time recluse, Mr. A. R. Black, who urges him to overcome his phobias.

Over six months, Oskar learns many things but not what the key represents, until he meets William Black, who sells the vase in which Oskar finds the key to Oskar's Dad just before 9/11. Learning that there is no more to the mystery than this, Oskar undertakes a project to dig up his Dad's empty coffin, to proclaim the truth that Dad is dead. Oskar's companion in this adventure is, he learns only later through letters from Grandma, his long-lost paternal grandfather, who flees his marriage before the birth of his son. He has been living with Grandma as a hidden renter since 9/11. Oskar shares his story with this stranger when he cannot find his Grandma one day, and confesses to William Black his guilty secret: that on 9/11 he is too petrified to pick up the phone to answer Dad's final phone call before the building collapses. Oskar dreams of everything on 10-11 Sep. 2001 running in reverse, so he can feel safe.