One morning at the farmers' market, metrology inspector He Tiemei takes enforcement action and confiscates a faulty steelyard from a vendor named Chang Dazhuang. However, she discovers that someone has secretly replaced the counterweight and ground off its steel verification mark. Following the clues, she uncovers a scheme orchestrated by market administrator Qin Suanpan, who secretly manufactures counterfeit verification marks, swaps out counterweights, and extorts money from new vendors. He Tiemei joins forces with the wronged Chang Dazhuang to stake out the market at night and gather evidence. They catch Qin Suanpan in the act and uncover a wider network of corruption spanning multiple markets through his account book. Despite entrenched personal connections and threats, He Tiemei refuses to compromise. She stands firm on the principles of metrological verification, investigates every market scam, and protects ordinary people's right to fair prices and honest measurements. Determined to continue, she heads to the next market to uncover the truth.