A mermaid from the Joseon period ends up in present-day Seoul, where she crosses paths with a swindler who may have ties to someone from her past.

Popular TV anchorwoman & late night radio host Sun-Young prepares to work her final radio program. After this program she will prepare to take her ill daughter to America the following morning. During the radio show Ko Sun-Young receives a startling text message. At Ko Sun-Young’s apartment, her ill daughter is being watched by Sun-Young’s sister Ah-Young. Then, a man named Dong-Su breaks into the apartment with a large wrench. He knocks Ah-Young unconscious, but is unable to locate Sun-Young’s daughter – who is hiding in a closet. Dong-Su then sends the text message to Sun-Young instructing her to follow his directions and not to tell anyone.