Fate of Cthulhu - Rules of Play says:
Fate of Cthulhu is a stand-alone game powered by the Fate Core System. No other books are needed to play. You are those one-way travelers from a dark future and their crucial allies from the present day, working together to save the human race from looming apocalypse. Armed with foreknowledge of Judgment Day, you must succeed at a series of vital missions aimed at restoring hope to the future. Can you defeat the vast unknowable evils of the Great Old Ones before you become a monster yourself?