Chemistry teacher He Jianwen finds himself caught in an intense conflict between his wife's extreme fear of bacteria and an elderly person's adherence to traditional ways, triggered by a jar of aged brine brought by his mother-in-law. Faced with his wife's terror of nitrite carcinogenesis and the crisis of the jar being dumped, He Jianwen issues a strict deadline military order, sets up a miniature fermentation station on the balcony, and vows to use rigorous data to vindicate the old taste. As white mold appears and suspicions of stray bacteria follow one after another, it remains hanging in the balance whether this old saltwater that sparked the dispute is a hidden hazard or a treasure trove of probiotics. He will use chemistry as his ruler to break cognitive biases, guarding his family's health and the warmth of everyday life.