"The subterraneans" and "Pic"

In a vase in a closet, a couple of years after his father died in 9/11, nine-year-old Oskar discovers a key ... The key belonged to his father, he's sure of that. But which of New York's 162 million locks does it open? So begins Oskar's quest, but will it take him any closer to, or even further from, his lost father?