Blood Rain( 혈의 누 ,Hyeolui Nu) is a 2005 South Korean film . It is a murder mystery set in 1808 during the Joseon Dynasty . This film touches on historical prejudice against Roman Catholicism in Joseon Korea .

It's early 19th century Korea. The film introduces with the depiction of Dongwha Island, an island in which most of its inhabitants dedicate on paper-making industry. One night, the paper cargo, set to be sent to the royal court, is burned by a mysterious fire.

The government sends officer Wonkyu to the island to investigate the incident. On the day of arrival, Wonkyu discovers that a murder had simultaneously happened on the night of fire. The villagers are terrified and in a state of panic, blaming the grudged spirits of family Kang to be the responsible force. The Kang was a family who had been all executed years ago by the government, after having been accused of being Christian converters.

While Wonkyu tries his best to gather the fragmented clues behind the incident, more atrocious murders occur, driving the villagers into a higher state of panic and some even to insanity. As the young officer approaches to the truth, digging deeper into the island’s dark past, Wonkyu discovers that there may be something even more frightening than the murders or the murderer on the island - a truth that will make him to question about the deepest part of our human nature.