Peter Dickinson's first three children's books, The Weathermonger, Heartsease and The Devil's Children, form a trilogy. They are all set in a Britain chronologically of the near future yet also of the past, for the 'Changes' have taken place, causing the country to become an island

… fragmented into a series of rural communities, united by a common hostility to machines of any sort and by a tendency to try to return to the modes of living and thought that characterized the Dark Ages….

This basic hypothesis, that Britain has changed in this way, provides the mainspring of the trilogy.

The other two books simply ask one to accept the Changes without explanation, and are more successful because of it. Heartsease takes place about five years after the Changes, and The Devil's Children is set at the very beginning of the Changes, when people are leaving in their thousands...