A mother lives quietly with her twenty-eight-year-old son, Do-joon, providing herbs and acupuncture to neighbors. One day, a girl is brutally murdered, and Do-joon is charged with the killing. Now, it's his mother's call whether to prove him innocent or to leave him imprisoned.

When an unknown toxic gas strikes Seoul in an unprecedented act of terror, Yong-nam has just met Eui-ju from college by chance at his mother's birthday banquet. The city falls under sudden noxious gas attack and together, they must escape the panic-stricken city.