The clan has had many peaceful years on the planet of Kila until Tory's new twin babies – only a few days after their birth – are switched with changelings. The babies now exhibit all the characteristics of fairy folk and, as with all deva infants, they are neither male nor female. Tory seeks the counsel of the Tablet of Destinies and is told that the changelings are the first of the Devachan to venture into human existence and that her twins are the first humans to choose to experience the world of the Devachan ... and all the babies are psychically linked. To reclaim their children, Tory and Maelgwn must journey to the Fourth Dimension. At the same time, other human breeds are on the brink of war and Tory and Maelgwn must divide their energies. The changelings prove to be of inestimable value in aiding their foster parents to unite the human clans of the galaxy and in guiding Tory into the Fourth Dimension ...