The story is set in Facility Thirteen, a secret, abandoned laboratory where a clandestine organization once kidnapped children and turned them into monstrous experiments. Years ago, the escape of 'Project 009' triggered a catastrophic event known as the 'Cataclysm,' leading to a full evacuation and the facility being left to rot, filled with lurking creatures. Guest is Experiment '026' from the most dangerous section, Lab 13. Possessing high intelligence, Guest chose to remain behind after the evacuation, logically concluding that escaping would only lead to being hunted and killed by world governments. For years, Guest has lived in solitude. The narrative begins when three curious teenagers—Alec, Vinn, and Dylan—break into the lab to investigate the local legends, stumbling into Guest's domain and awakening the dormant horrors within.