A girl is found murdered. A mother's handicapped son stands accused, but she will stop at nothing to prove his innocence. Hye-ja plays a single mum to 27-year-old Do-joon. Though an adult in years, Do-joon is like a child and dependent on his mother, sometimes behaving in ways that are stupid or simply dangerous. One day a young girl is found dead in an abandoned building and Do-joon is accused of her murder. An inefficient lawyer and the apathetic police force that close Do-joon's case too quickly inspire his mother to act on her own - to act as Mother in its purest form. Summoning all her maternal instincts and trusting no one, she sets out to find a killer and prove her son's innocence; no matter what the cost.