The ambitious and successful lawyer Do Hae-gang (Kim Hyun-joo), and her husband, Choi Jin-eon (Ji Jin-hee), have a dysfunctional relationship. They lose their child and Jin-eon starts an affair with a much younger girl, Seol-ri (Park Han-byul). Dokgo Yong Gi is Do Hae Gang’s unknown twin sister. After the couple divorce, Hae Gang gets into a mysterious car accident and loses her memory. Baek Seok (Lee Kyu-han), mistaking Hae Gang as Yong Gi, saves Hae Gang and makes her live as Yong Gi. Hae Gang becomes Baek Seok’s fiancé and lives with his family. What will happen when Jin Eon and Hae Gang meet again? Will the couple be able to go back to how they used to be before?