Jung Seop, the only son of a rich man, is killed in a train crash. Yun Hui is one of the surviving passengers. But she is mistaken as Jung Seop's wife. Living with his parents, she gives birth to a son. Jung Seop's parents love her more, thinking her son is their grandson. But Yun Hui always feels guilty for deceiving them. When she finally confesses her secret, Jung Seop's parents forgive her and say they want to live with her.