It is 1788 and King George III has succumbed to a deepening bout of madness. Doctor Francis Willis has been summoned from his asylum in Lincolnshire to treat the King only to find that it is no medical malady that tortures His Majesty, but rather twisted mythological Celtic magic. He leads the effort to lift the curse on the King and restore the realm to sane governance before the King is forever lost to madness and the realm descends into chaos.