Nine-year-old Oskar Blum is an inventor, amateur entomologist, Francophile, letter writer, pacifist, natural historian, percussionist, romantic, Great Explorer, jeweller, detective, vegan, and collector of butterflies, Beatles memorabilia, state quarters, miniature cacti and coral. When his father is killed in the September 11th attacks on the World Trade Center, his inward journey towards some kind of peace takes him on an odyssey through the five boroughs of New York, as he attempts to solve the mystery of a key he discovers in his father's closet . . .