'The Beast' is a tense murder mystery / action thriller about two detectives in conflict who have to team up to solve a gruesome murder. After the mutilated body of a missing girl is discovered in the tidelands of Incheon, Han-su and Min-tae, who have been rivals for years, are now in charge of finding the culprit. The case seems like it will find a quick resolution with a suspect in custody, but things take a dark turn when Han-su meets an informant who insists that he knows who the murderer is. As cover-ups and secret deals ensue, tension rise between the two detectives as the pressure of solving a crime is shaking up the Korean peninsula comes to a head.