Since her father favored boys over girls, Jeong-in (played by Shin Hye-sun) ran away from home in middle school and lost contact with her family. Jeong-in later became a top defense lawyer on her own. By chance, she learned that her mother, Hwa-ja (played by Bae Jong-ok), who suffered from Alzheimer's disease, was suspected of killing her father and also murdering many innocent people. Jeong-in, who suspected something was fishy, decided to take action herself. With layers of obstruction, how could she change her mother's confession and uncover the unspeakable truth behind this murder case?