The concluding part of the captivating Sangreal trilogy from the author of Prospero's Children.
In the azure gloom he saw the island, not floating on the surface but moving through deep water, the rose-stained boulders swelling and shrinking like the bulb of a vast jellyfish. A skein of tentacles trailed behind it, fifty yards long or more. Something pale was tangled in their grasp, something that barely struggled now. He wrenched his thought away in horror, out of the sea, out of the dream, through the veils of sleep to his own world.

Like most young people, when Nathan Ward sleeps, he dreams of adventure; of worlds beyond conscious imagination; of becoming a hero destined to overcome some lurking fear. But unlike most people, Nathan cannot relish such escapism, for his dreams are not fantasies; his journeys are real and the nightmares he faces can keep him from ever waking up.

But Nathan cannot rest until he has found all three components of a great spell, each hidden upon a different alien world. The last piece is still missing, lost upon an oceanic planet infested with aquatic beasts.

If he survives the mysteries of the deep, Nathan will be forced to confront the architect of his fate. For recovering the last item will reveal the true purpose of the great spell and make clear the intent of its creator. Nathan believes it will save all the worlds that he holds dear, but it may also demand a terrible sacrifice; one that Nathan has no choice but to pay.