When a sudden, inexplicable societal shift turns England against all forms of technology, a young man named Geoffrey finds himself branded a witch for attempting to repair a motorboat. Geoffrey and his sister Sally must navigate a landscape defined by fear, superstition, and the rejection of modern progress. As they flee to France and eventually return to their homeland, they operate under the constant threat of persecution from a populace driven by irrational hatred. The narrative follows their quest to uncover the source of the mysterious spell that has regressed their country into a primitive state.

This work is frequently noted for its unique premise that blends elements of science fiction with a folk-horror atmosphere. The narrative is often praised for its ability to maintain a sense of unease while exploring the consequences of a society that has abandoned its technological foundations. Readers often highlight the stark contrast between the characters' experiences in a normal France and their struggle within the isolated, regressed England. The book remains a significant example of speculative fiction that challenges the assumption of linear progress in civilization.