During the Great Depression, Martin, a 12-year-old only child of Nashville, Tennessee, has lost his father to polio and his mother has become overbearing. She hires a World War One veteran, Seth, to work at their home. Unbeknownst to her, Seth suffers mental illness. When he drives Martin's beloved dog Fritz away, the boy has had enough loss. Martin goes against his mother's wishes and sets out to find Fritz, an odyssey that takes him into dangerous, unknown territory. He finds power-hungry men seeking a mysterious cache of futuristic weapons—the Will'ven't Bin—and are willing to kill anyone who stands in their way.