One year after their son's death, Seiichi Kirishima and his wife, Miki, choose to take an island vacation in an attempt to forget their past. For Seiichi, however, this trip is merely a pretext: he intends to murder Miki and begin a new life. When he attempts to lure her to a secluded spot, she manages to escape into a foreboding cave. After pursuing and disposing of Miki, Seiichi believes the matter is settled, until he comes face-to-face with a ruthless, grotesque creature. Compelled to flee further underground, Seiichi quickly understands that a return to normalcy is impossible, witnessing terrifying scenes as his imminent death draws near.