2019 year. Seo-yeon, 28, returns to her home in the countryside. The father died a long time ago, and relations with his mother, who is in the hospital, did not improve. Seo-yeon lost her cell phone, so she turns on the landline and starts getting strange calls from the girl asking for help. It turns out that the stranger's name is Yong-suk, she is also 28 years old, and she lives in the same house, but in 1999.