Lin Rui, an eighth-grade fitter, stands firm on product quality standards. After refusing to approve substandard gears, he clashes with the factory director and leaves after making a wager. With his apprentice, he hand-grinds components in a crude mud hut. The apprentice is once bribed into stealing blueprints but later comes to his senses. Together with a former quality inspection chief, they tackle technical challenges and use their exceptional craftsmanship to produce gears that meet standards, proving through real-world tests that they outperform inferior products. They uncover evidence of illegal profiteering, and those responsible are dealt with according to the law. Lin leads the team in optimizing production and revitalizes the factory through the spirit of craftsmanship.