A group of inexperienced young engineers travel to Colorado to join a railroad construction camp, eager to learn practical skills and prove themselves. They encounter colorful frontier characters, including a dangerous outlaw nicknamed Bad Pete and a scheming trouble-maker who works against the road. Daily toil, field work, and tests of courage push some boys into acting leadership as responsibility replaces inexperience. As sabotage, ambushes, and legal threats mount, the young crew helps uncover conspiracies, lay traps, and defend the line, leading to the exposure and defeat of those trying to wreck the railroad's prospects.