One by one, the crafty members of a destitute family insinuate themselves into the household staff of a wealthy couple living in oblivious privilege.

Ancient Korea, 1506. The tyrannical King Yeonsan-gun of Joseon is overthrown by his half-brother Jung-jong, whose reign begins with a blood bath. Over the years, traitors plot against him, sinking the kingdom into chaos. In 1528, frightened rumors come to royal palace, regarding a mysterious creature, known as Monstrum by the peasants.

Two apathetic police academy recruits who become best buddies through the tough training together witness a woman being abducted right before their very eyes. As they were taught in the academy, they quickly report the incident to the police, but the police are in no hurry to jump on the case. So the duo decide to take the matter into their own hands and rescue the woman.