A chance car switch alters the lives of twin sisters separated for 30 years. Hae Kang, a successful but emotionally distant lawyer, is reeling from the loss of her daughter and a crumbling marriage to Jin Eon, heir to a major pharmaceutical company, who has fallen for another woman, Seol Ri. Just before their divorce is finalized, Hae Kang unknowingly swaps cars with her twin Yong Ki—a pregnant widow trying to uncover the truth behind her husband's mysterious death.

When Hae Kang gets into a severe accident in the switched car, she loses her memory. She's rescued by Baek Seok, who mistakes her for Yong Ki, his first love, and takes her in. Now living as Yong Ki, Hae Kang transforms into a warm, cheerful woman. As Jin Eon prepares to marry Seol Ri, he encounters her again—confused and drawn to this changed version of his wife, while Hae Kang is left shaken by feelings she can't explain.