Su Heng is Linchuan's only licensed chief engineer and the son of Huanyu Group's chairman, living incognito at Panshi Construction for experience. On a rainy night, he signs to save an unfinished project, but his credit is stolen by the boss's nephew, Fang Lie, and he is humiliated and fired. He could have revealed his identity and walked away, but he discovers a fatal crack hidden in the East City building, and Panshi used inferior reinforcing bars. To protect the lives of four hundred households, he endures humiliation and stays to investigate, until his wife is pushed down the stairs while protecting the construction log. At the signing ceremony, he calls out "Dad" in public. His pen is more expensive than their money.