From the publisher's website:
It is the roaring 20‘s, and while there’s electricity in the air, unnatural storms are brewing as well. Strange things are happening in the small Massachusetts town of Arkham: people have gone missing, sightings of indescribable creatures grow more and more frequent, the very air thickens with a sense of foreboding that roils like an acrid mist through the streets. The Ancient Ones are stirring... Designed for 1-8 players, Arkham Horror is a cooperative adventure game of survival, horror, and investigation. A terrible creature from beyond time and space – an Ancient One – is awakening, roused by dimensional gates that are opening all over the city. Players take on the role of investigators, each with a unique backstory, abilities, and equipment. Joining forces, the investigators must secure the city, encountering its haunted and mysterious locations before the Ancient One awakens. If the Ancient One awakens and defeats the players in the final battle, all of Arkham is doomed.