天狩三年,皇太子宋泠遇刺身亡,史称“刺棠”案。与太子青梅竹马的名相之后苏落薇为调查此案真相,嫁与太子爱弟宋澜为皇后,谁知随后她竟发现此案竟是宋澜为夺嫡所设的毒计。为匡扶朝纲、替爱人复仇,她决意利用北归的天子近臣叶亭宴,却不知此人正是以为她背叛了自己的太子本人……
In the third year of the Tian Shou era, Crown Prince Song Ling was assassinated, an event known as the "Thorn of Tang" case. Su Luo Wei, the daughter of a renowned minister and childhood sweetheart of the Crown Prince, marries Song Lan, the Crown Prince's beloved younger brother, to investigate the truth behind the case. However, she later discovers that the assassination was a treacherous plot orchestrated by Song Lan to seize the throne. To restore order to the court and avenge her lover, she decides to use Ye Ting Yan, a close advisor to the Emperor who has returned north, unaware that he is none other than the Crown Prince himself, who believes she has betrayed him.