Hunting for a bird injured on a pheasant hunt, Arby telepathically hears a voice calling for help. He finds a pallid, golden-haired youth with solid blue eyes under a pile of leaves, and takes him to (relative) safety.
Arby's sister Jane finds them. Sky tries to explain that the world is treating him as an infection and trying to expel him: he needs to find a Juganet to enable him to return to his own time.
The forces trying to eject Sky condense into the ruthless, menacing form of Goodchild, who causes Arby's mother to be hurt in an accident. Sky tries to help, but puts himself in jeopardy.
Finding Sky unconscious, Arby, Jane and their friend Roy rush him to hospital, where his life is put in further danger by Goodchild. However, he may be closer to finding the location of the Juganet.
With the help of a simple-minded patient, Sky escapes and they all travel to Glastonbury Tor. A hippy couple believe Sky to be the last of three mythical messiahs until Goodchild, and the planet's forces (the animus), attack again.
Finding a safe place for Sky to recover, Arby and Jane are lured away and trapped. Goodchild tries to attack Sky again - but Sky has now metamorphosed into his true form.
Sky finally finds the Juganet and prepares to travel to his appointed time to assist the future humans who have rejected technology. Arby follows him, only to find his own life in jeopardy.
