On the night of Lantern Festival, a talented young man from Chang'an, Li Yi, recovers a purple hairpin that has been dropped by Huo, the woman of his dreams. Moved by his sincerity, Huo's mother agrees for the two to get married on that very night. Li then seals the vow of eternal love to her in blood letters.
Although he has passed the imperial examination, Li is appointed to a position beyond the Great Walls after failing to pay homage to Lu, a senior official in charge of military affairs. Lu sees to it that nothing should beheard from Li for three years, during which Huo falls gravely ill and lives by pawning her jewelry.
Lu summons Li back to Chang'an with the intention of forcing the young man to marry his daughter. Lufurther procures the purple hairpin pawned by Xiaoyu and shows it to Li as proof that his fiancée has remarried. Li is convinced, but swallows the hairpin to show his determination not to marry Lu's daughter. Infuriated, Lu threatens to accuse Li of expressing treacherous ideas in his poems, leaving him no choice but to comply. Upon hearing her husband has betrayed her, Huo vomits blood.
With the help of “Yellow Gown”, a chevalier in charge of military affairs, Huo reunites with Li, clearing up all misunderstandings. When Lu has his men take Li to his house by force, “Yellow Gown” orders Huo to break into the house to claim her husband. It turns out that the yellow–gowned chevalier is the emperor's brother. The chevalier deposes Lu in the name of justice. Huo and Li Yi are finally reunited.