Su Wan has just married into a marquis's household with strict rules when her mother-in-law, Shen Jingshu, puts her through an intensive “onboarding program.” Thanks to her modern-day emotional intelligence and powers of observation, Su Wan realizes that her mother-in-law is a brilliant manager who isn't happy, and that certain details, such as the way she keeps the accounts and deals with disobedient servants, reveal a decisiveness and intelligence far ahead of her time.
One day, Su Wan casually improves the household's tedious catalog of utensils with simple modern illustrations. Shen Jingshu sees them and scolds her for “frivolous tricks,” but later that night, she sits alone, lost in thought as she studies the catalog. Catching this moment, Su Wan realizes that her mother-in-law isn't a decaying symbol of feudalism, but an intelligent woman buried by her era.
When a crisis hits the household, such as a rival sabotaging its business or a major accounting error, Su Wan quietly helps her mother-in-law resolve it perfectly with modern crisis management and logical analysis. Stunned by Su Wan's perspective and methods, Shen Jingshu finally lets down her guard. The two share a conversation beneath the moonlight that goes beyond their roles as mother-in-law and daughter-in-law. Their alliance is born.
