Paul Atreides has been succeeded by his twin children Leto and Ghanima, under the regency of his sister Alia But all is not well in the Empire a harsh tyranny has been established under the fanatical direction of the Fremen disciples On Arrakis itself, much has changed A slow ecological transformation has brought vast areas of greenery and even stretches of open water The sand-worms are vanishing and this spells disaster for the planet