Cass Dunreith drives a VW GTi, lives in Brooklyn, and makes her living writing comic books. But once a year she becomes Lady Siobhan, renowned far and wide for her bravery and skill. On a massive campground in Pennsylvania, her medieval fantasy society holds its annual summer War. Here, as always, Cass will wander among the colorful participants dressed in medieval garb - jugglers, peddlers, courtesans, artisans, and knights - enjoying a delightful respite in a world of make-believe, culminating in a mock battle. But this year the fantasy will become a grim reality when an implacable army of gray-faced horsemen from the mists of Celtic legend is unleashed on the weekend warriors. Suddenly Cass finds herself in a world where the swords have real edges and people can die - and only one person stands between fantasy and a bloodbath: herself.