After Becoming a Substitute Bride, I Audited the Marquis's Household for Three Years

Shen Yizhen, the illegitimate daughter of a merchant family, is pressured by her stepmother into taking her elder sister's place and marrying Pei Su, the marquis's heir, who is rumored to be near death.

Everyone expects the wedding to fail to bring him good fortune and for her to become a widow.

On their wedding night, Shen Yizhen discovers that this frail heir, who can barely get out of bed, sneaks out through a window in the middle of the night to kill people.

At the same time, drawing on the bookkeeping skills she honed by checking her family's accounts since childhood, she discovers in the marquis's ledgers that tens of thousands of silver taels go missing every year from this seemingly declining estate. The money is connected to a massacre that wiped out the Shen family ten years ago.

One pretends to be ill while investigating a case involving military pay, and the other pretends to be foolish while investigating her mother's death.

At first, they test and use each other. In the end, they become the only people either can trust with their back.