After getting divorced, Eun-su left for America with her daughter Su-a. Three years later she decides to return to South Korea. They can’t wait to go home, but Eun-su’s parents are away on business. Having no better choice, Eun-su decides to live in their empty house with Su-a.

One day Eun-su realizes that Su-a is missing when she came home from the grocery store. Eun-su searches frantically for her daughter and receives a message that her parents took Su-a. Eun-su quickly calls her parents, but they don’t answer the phone, just send the photo of Su-a. While waiting for her parent’s call, strange things begin to take place around Eun-su. A stranger greets her as if they were acquaintances. A security guard gives her a strange mobile phone saying that it is hers. An old college friend shows her a photo, saying that they saw each other in previous year. In confusion, she receives a letter from her parents. It says, “Su-a is well. Don’t worry about her. Send us some money.” With no choice, Eun-su asks her ex-husband for help.

Her ex-husband Yeon-ho tells Eun-su a shocking truth, which drives Eun-su to a situation in which she can trust no one but herself. And she even faces a woman who has the same face as her. Eun-su and Yeon-ho begin to track down the truth. Learning that all these incidents are related to Eun-su’s childhood, they trace the past. Who took her daughter? Who am I? Who is she? She has to suspect everyone if she wants to get her daughter back!