Skara Brae, Orkney, during the Neolithic period. The sun is dying, crops are failing and the local inhabitants fear that the end of the world is near. When a strange boy appears from nowhere, dressed in an odd silver suit - his 'silver skin' - the community is thrown into confusion. Who is he, where is he from, and why has he come? Is he a selkie or seal person, a mythical being believed to have magical powers?

For Cait, herself an outsider in the community, the boy, Rab, arouses a strange fascination as she finds herself strangely drawn towards him. For Voy, the Old Woman, Rab represents the only hope for the sun's regeneration, but only if his silver skin is burnt in a huge sacrificial blaze. As the pyre is built, Rab must fight for his life if he is ever to be able to return to his own time. And if he succeeds, what will be the fate of the islanders he will leave behind?