Waterproofing master Chen Yu is dutiful and adheres strictly to principles, always insisting on signing a contract before starting any engineering project. His third uncle wants to skip the process out of a sense of relational courtesy, expecting to rely on family ties to make Chen Yu bear subsequent risks, but is rejected by Chen Yu. Family members find it hard to understand and start harboring grievances against him. When the project eventually encounters quality hidden dangers, various conflicts completely erupt. Chen Yu takes out the preserved communication vouchers to clarify the responsibilities of all parties. Human favors are human favors, but doing things according to the rules is the best way to resolve conflicts.