Eefa and her twin brother, Magio, are on the run, hunted by a ruthless predator with a pack of terrifying wolf hounds. They have no idea why this is happening to them. Until recently they enjoyed a carefree life in the ramshackle town of Warren on the semi-tropical isle of Moon. Since birth Eefa has been invisible to everybody other than Magio, an invitation, as Magio sees it, to adventure, inspired by the tall tales of their lodger, Quimbre. But now the sudden death of their beloved Gran has turned their world upside down. Out of the blue, terrifying giants attempt to kidnap Eefa, who is rescued by the intervention of an eccentric old woman the locals call “Bird Woman”. And now Bird Woman insists that Eefa and Magio are no longer safe. They must abandon their childhood home and flee to the Valley of the Raptors, high in the snow-capped mountain peaks of Moon.

What fate awaits the twins in the Valley of the Raptors? Will Eefa truly learn the reason for her invisibility? Will she and Magio escape from the vicious forces that are closing in about them – or is it really a malevolent trap?