Fear Itself

Fear Iself is a RPG book by Robin D. Laws that expands on the GUMSHOE investigative rpg system, first featured in The Esoterrorists. It is a horror game that plunges ordinary people into nightmarish dangers and violence.

Both The Esoterrorists and Fear Itself can be further expanded with The Book of Unremitting Horror, which is a sort of monster manual/scenario ideas supplement.