Kim Ji-Young (Jung Yu-Mi) has one of the most common female names for people her age. She works at a PR agency. Kim Ji-Young gets married and has a daughter. So she can raise her daughter, Kim Ji-Young quits her job. She leads an ordinary life up to this point. Suddenly, Kim Ji-Young begins to talk like her mother, her older sister and other people. She seems possessed by other people. What happened to her?