The King's Warden

Yi Hong-wi, the teenage king of Joseon, is overthrown by his uncle, Grand Prince Suyang, and demoted to Prince Nosan. The powerful official Han Myŏnghoe sends the former king into exile in the hopes that he would commit suicide. Eom Heung-do is the chief of a poor village in the mountain valley of Cheongnyeongpo in Yeongwol. After visiting a neighboring village, which became prosperous after sheltering an exiled (later reinstated) aristocrat, he convinces his villagers to do the same after hearing the news of an exiled nobleman coming to the region.

Heung-do's village is chosen as the place of exile for Prince Nosan due to its remote location. Nosan arrives with his loyal maid Mae-hwa. The villagers become anxious when they learn the true identity of Nosan, who is haunted by the memory of his loyal court officials who were brutally executed for opposing the new king. He grows suicidal and attempts to jump off a cliff, but is saved at the last second by Heung-do. Grand Prince Kŭmsŏng, another uncle of Nosan, secretly contacts him about an upcoming revolt to restore him to the throne.

Heung-do oversteps and angrily chastises Nosan after mistaking him to be attempting another suicide. The commotion lures in a tiger which threatens them and the villagers. Tae-san, Heung-do's son, shoots the tiger with his hunting bow. Nosan draws the attention of the tiger and shoots it in the head, killing it. The incident brings new life to Nosan after he contemplates the perspective of Heung-do and his villagers. He begins to bond with them, and starts teaching Tae-san to prepare him for the Civil Service Exam.

Myŏnghoe becomes aware of the plot to restore Nosan to throne. When Tae-san visits Nosan's residence without permission, Myŏnghoe has him punished by flogging. Heung-do and Nosan try to intervene, but Myŏnghoe mocks Nosan's status as an exile and his lack of authority.

On the night of the revolt, Nosan escapes from his residence to join forces with Kŭmsŏng. Heung-do attempts to convince Nosan against leaving, but Nosan appeals to his newfound desire to take control of his destiny. Heung-do escorts him to the rendezvous location, where they and Kŭmsŏng's forces are ambushed and captured by Myŏnghoe's troops. Nosan pretends to accuse Heung-do of betrayal to save him and his village from destruction. The plot fails after Kŭmsŏng and his followers are captured.

Nosan and Kŭmsŏng are sentenced to death by royal decree via poisoned drink. Wishing to die on his own terms, Nosan convinces Heung-do to kill him instead. On the day of the execution, Heung-do mournfully strangles Nosan with a bowstring. Nosan's body is unceremoniously thrown into a river, and Mae-hwa jumps to her death. Heung-do secretly recovers Nosan's body from the river and gives him a burial.

The notes at the end of the movie state that 241 years after Yi Hong-wi's death, he is posthumously reinstated as King Danjong. Heung-do is celebrated for his loyalty and righteousness and their respective tombs still lie in the same place today.