Seo-jin is a widower still grieving his wife's death. Then he receives the news that his long-lost younger sister, Yoo-jin, who went missing 25 years ago, has turned up. Unlike the rest of his family, who welcome her into their arms, Seo-jin feels that Yoo-jin is a stranger. Seo-Jin is a popular architect. He suffers from a trauma when his younger sister Yoo-Jin went missing. 25 years after her disappearance, Yoo-Jin comes back to her family. Seo-Jin feels something is not right with Yoo-Jin.