T.S. Spivet lives on a ranch in Montana with his mother who is obsessed with the morphology of beetles, his father (a cowboy born a hundred years too late) and his 14 year-old sister who dreams of becoming Miss America. T.S. is a 10 year-old prodigy with a passion for cartography and scientific inventions. One day, he receives an unexpected call from the Smithsonian museum telling him that he is the winner of the very prestigious Baird prize for his discovery of the perpetual motion machine and that he is invited to a reception in his honor where he is expected to give a speech. Without telling anyone, he sets out on a freight train across the U.S.A. to reach Washington DC. There is also Layton, twin brother of T.S., who died in an accident involving a firearm in the family's barn, which no one ever speaks of. T.S. was with him, measuring the scale of the gunshots for an experiment, and he doesn't understand what happened.

Avid movie-watcher and video store clerk Bazil has had his life all but ruined by weapons of war. His father was killed by a landmine in Morocco and one fateful night a stray bullet from a nearby shootout embeds itself in his skull, leaving him on the verge of instantaneous death. Losing his job and his home, Bazil wanders the streets until he meets Slammer, a pardoned convict who introduces him to a band of eccentric junkyard dealers including Calculator, a math expert and statistician, Buster, a record-holder in human cannonball feats, Tiny Pete, an artistic craftsman of automatons, and Elastic Girl, a sassy contortionist. When chance reveals to Bazil the two weapons manufacturers responsible for building the instruments of his destruction, he constructs a complex scheme for revenge that his newfound family is all too happy to help set in motion.