When the sleepy town of Weyharrow is enveloped by a mysterious fog, the inhabitants find themselves behaving in strange and dangerous ways. Dr Steven Glaze, a young probationary GP, prescribes a most unorthodox treatment for arthritis; the vicar proclaims in morning service that the villagers are in the hands of the devil; and Phyllis Knabbe tragically commits suicide. Throughout the village people have seemingly taken leave of their senses.Soon word leaks out and Weharrow becomes inundated both by the national press and a bus load of hippies seeking a magical experience, who believe that a nearby ancient pagan temple is somehow responsible for this strange phenomenon. But Steven Glaze and Jenny, a reporter for the local newspaper, feel sure that there is more to this than meets the eye and they set out to discover the cause - supernatural or otherwise - of everyone's drastically altered behaviour.