Leo leaves school and starts work on a construction site. He wants an office job, so the site is a surprise. He knows many rules. But he does not use the rules, and he feels slightly unhappy.
An old man, Xu, runs the site. Xu is a good storyteller, so young men sit with Xu at lunch. Xu talks about Wang Yangming, a teacher of the Ming era. The teacher left one simple concept: knowing and doing are one. And doing is the end of knowing.
Leo laughs at the old words. But the site brings trouble, and the trouble is a wall. The construction team builds a wall, and Leo reads the plans. Leo reads them twice, and his face turns red. The wall is slightly short. And the short wall comes from a small slip in the plans.
The team fixes the wall, but the work loses a week. Xu says nothing to Leo. But Xu's quiet voice makes Leo look up. "Knowing lives in the work," Xu tells Leo. His words motivate Leo, and Leo stays on the site.
Now Leo looks at every wall each morning. The wall work makes Leo tired, but he volunteers for more. When the weather turns cold, new men come to the site. And Leo sits with the new men at lunch.
Leo is not a good storyteller, but he tries. Leo tells the new men about the small slip in the plans. His story motivates two young men, and the two men stay. Then Xu smiles at Leo, because knowing and doing now meet in one man.