Cecilia, the legitimate heiress of the Winston family (second female lead), is the unattainable first love (mistakenly identified savior) of Lyon (male lead), the head of a multinational conglomerate. Since Cecilia is already engaged, Lyon has no choice but to treat her look-alike stepsister, Isabella (female lead, an illegitimate daughter), as his substitute girlfriend, subjecting her to all kinds of humiliation and torment. Three years later, as Cecilia's wedding approaches, news arrives that her fiancé, Evan (second male lead), is seriously ill. Cecilia wants to swap marriages with Isabella and marry Lyon instead. Isabella agrees to the swap in exchange for 100 million and marries Evan, a hereditary duke. On the wedding day, when Lyon discovers that the bride is not Isabella—the woman who had been by his side for three years—he is utterly devastated.
