Plagued by a realm left defenseless after his predecessor's purges, the new emperor Yan Lin faces crises at home and abroad. To shield the general's son, Nan Chenxiao, who hides in female disguise, and Rui Yu, who serves in court as a man, Yan Lin ordains a marriage between them, seeking a new variable in the desperate situation. Through shared trials and life-and-death journeys, the two uncover each other's secrets, kindle a hidden love, and ultimately help Yan Lin usher in a prosperous age.