Korea, 1728: After losing a battle, the once proud swordsman Kim Ho is demoted to a simple night watchman in a notorious prison. However, his martial arts are urgently needed there, because on his first night he suddenly finds himself face to face with Do Man-cheol and his battle-hardened followers, who want to free the rebel leader Lee, who has been sentenced to death. Kim vows to stop them at all costs - and gets into a series of merciless duels!