Gyeong-ah is employed as a caregiver and resides alone. She used to rely on her daughter, Yeon-su, but ever since Yeon-su moved out, it has become difficult for Gyeong-ah to see her. On the other hand, Yeon-su, who is going through a tough time due to her ex-boyfriend, Sang-hyun, gets into another argument with him and decides to visit her mother's house. After Yeon-su leaves, Gyeong-ah receives a startling message from an unknown individual.