8 years ago... Detective Cheon Do-cheol lost his daughter and wife to an unidentified creature. In order to hold on to even a thin thread of hope, he continued to investigate violent criminals. It seemed as if 8 frustrating years had passed by like that. However, his watch, which had been stopped, starts moving again when an unidentified female detective, "Ji Soo-won," enters Cheon Do-cheol's own department, the "Special Civil Affairs Division." And at the same time, Ahn Ha-ri, a young man who has lost all his dreams and hopes and heads to the sewers, sees a giant monster underground that swallows up his team leader and senior in one bite and says, "If you want to live, make a contract with me." The secret that had been hidden for 8 years finally comes to light.