Su Jinnian, a daughter born to a concubine, is forced to take her elder sister's place in marriage. Facing her sister's disdain and the servants' bullying, she neither cries nor makes a fuss. Instead, she uses an old account book to seize control of the General's Residence. She purges corrupt officials and hidden traitors, helps General Xiao Yan expose the truth behind his feigned illness, and uncovers a major military funds scandal together with him. When the border is in danger, she devises a strategy to cut off the enemy's grain supplies and secure the rear. Through intelligence and responsibility that transcend her humble birth, she rises from a despised substitute bride to a third-rank imperial-appointed lady, writing an extraordinary story of a woman who earns her place through her own abilities and protects her homeland.