A year after the death of their son, Seiichi Kirishima and his wife, Miki, decide to go on an island vacation to forget their past. For Seiichi, however, that is just a pretext: he plans to kill Miki and start life anew. When he tries to lure her to an isolated location, however, she gets away to an ominous cave. After following and getting rid of Miki, Seiichi thinks everything is over, until he encounters a merciless, gruesome creature. Forced to escape deeper underground, Seiichi soon realizes that there is no return to a normal life, experiencing horrifying sights as his impending demise approaches.