The bad-tempered grandmother Wu Mo-shun (played by Ra Won-ki) runs a coffee shop and believes she has a dutiful son who is a professor (played by Sung Dong-il), which makes her domineering. Everyone hates her, including her daughter-in-law, except for the old servant Park (played by Park In-hwan), who genuinely cares for her. When her daughter-in-law is hospitalized, the whole family, except for her grandson Ji-ha (played by Jung Jin-young), agrees that she should be sent to a nursing home. Feeling dejected, grandma Mo-shun goes to a photo studio to take her own epitaph photo, but unexpectedly, the photo transforms her into her younger self. The young Mo-shun, renamed Wu Do-ri (played by Shim Eun-kyung), starts a new life and even rekindles her dream of becoming a singer. Do-ri, being unique and unorthodox, is welcomed by everyone and even attracts the admiration of a TV director (played by Lee Jin-wook). However, her identity faces the threat of being exposed. She must make a difficult choice: to stay at 20 and enjoy life or return to reality and face her life.