Transmigrator Xu Changqing takes away the incognito Great Tang Princess Changle, Li Lizhi, and founds a nation to become emperor in the Southern Ocean overseas. Eight years later, their seven-year-old daughter Xu Qinghe, to seek relatives for her mother, single-handedly steers the 'Pojun' battleship to secretly return to Chang'an, bombarding open Vermilion Bird Gate with a single shot to break into the palace and recognize her family, and is recognized by Li Shimin as his granddaughter. Xu Changqing and his wife subsequently pursue her to Chang'an; Xu Changqing adopts the alias 'Xu Qing', and sneaks into the imperial palace under the guise of Princess High Sun recruiting bodyguards, secretly approaching his daughter. However, Li Shimin and his wife gradually grow suspicious and conduct covert surveillance; the jealous Zhangsun Chong sets a trap and abducts Xu Qing's wife—Princess Changle's identity is in imminent danger, and the family reunion and crisis explosion are on the verge of breaking out.