Sum is a developer for the social-connecting app "Somebody." Even though she has difficulty communicating with other people, she is friends with Mok Won and Ki Eun. Her friend Ki Eun works as a detective. A murder takes place, and the app "Somebody" is involved in the murder case. Architectural designer Yoon O appears in front of Sum and her friends. Yoon O is an attractive man, but he seems to be hiding something. Meanwhile, Ki Eun investigates the murder case with the help of Mok Won.