One summer, during the dark days of World War II, eleven-year-old Antonio becomes a traquero. He works alongside his father, grandfather, and other Mexican and Mexican American men building and repairing the railroad tracks that run across America. Antonio meets Luis, a fellow traquero not much older than himself who traveled from Mexico to work on the tracks. Alone and a long way from home, Luis is grateful to find a friend in Antonio. Suspecting there are hidden treasures stashed away in a secret location, the two boys become sleuths and set out to uncover them. What they discover turns out to be far more valuable than gold or precious gems.