From the Introduction:
This is a role playing game to support the solving of supernatural mysteries and the hunting of paranormal creatures in out modern world in the tradition of episodic TV shows. Each adventure should be considered an episode, while the overall campaign is the "season", ending with the season finale, of course.
Characters take on the role of "hunters", people who know the truth and have given up their normal lives to find and stop preternatural and paranormal creatures and save as many people as they can.
Preternatural is about mysteries and action. Hunters are trained individuals who first investigate to find out what is going on and what they are up against, and then do their pest to destroy it once and for all.