On the wedding day, the original groom Alexander vanishes into thin air. Isabella, heiress of the Windsor Jewelry Group, is forced to accept a contract marriage with a stranger, Leo, who steps in as a temporary replacement, in order to save her debt-ridden, near-bankrupt family. After the wedding, Leo plays the role of a humble, submissive househusband mocked by high society. But Isabella stumbles upon clues and realizes with shock that this seemingly worthless husband is none other than the mysterious billionaire avenger Mr. X, who single-handedly caused the Windsor family's crisis — and this marriage was the final piece of his revenge plan. The roles of hunter and prey reverse: Isabella dons a mask, feigning to maintain the marriage while secretly plotting to short Black Group, probing step by step for his weaknesses. Just as Leo develops real feelings and decides to let go of his hatred and cancel the debt to grant Isabella her freedom, Isabella's revenge plan can no longer be stopped. A marriage born of deception and transaction evolves into a battle of wits between two highly intelligent powerhouses. And neither realizes that a true enemy still lurks in the shadows — a dusty vintage wedding ring that will unveil every buried secret.
