Lin Wan, an expert from the Agriculture and Rural Affairs Bureau, returns to her hometown to reform the aquaculture ecology, unexpectedly having her sister bitten to miscarriage by a foreign snake smuggled by the evil neighbor Zhao Guangfa. Making no fuss or noise, she uses "exercising duties according to law" as her main lethal move: sampling, testing, reporting, and on the big delivery day law enforcement seals the snake farm, making the evil neighbor lose everything on his road to wealth. Her sister's justice is reclaimed by rectification according to law.