Police trainee Mooyoon starts his career in law enforcement in a quiet suburban town only to notice stray cats and dogs disappear mysteriously. A joint rescue operation between the police station and the fire station brings him close to Taeyi, a young firefighter who happens to be his next-door neighbor. Together, the two begin to track down leads that unravel a much larger menace. As the mystery intensifies, their bond only grows stronger... until an unthinkable tragedy strikes.