Simon Bradley, a highly imaginative child, brain-damaged after a bizarre attack, vanishes one day from his home. Months later a body is found on the edge of Ryhope Wood. The wood shields a heart of primeval forest wherein live phantoms and strange creatures - mythagos - those shades generated over time by our dreams and nightmares.
Alex has in fact been absorbed by the wood, drawn into its green heart - through a 'hollowing'. There his dreams will continue to populate the wood with its mythagos. But like Alex, they too are damaged: the great heroes he conjures are warped, incomplete and dangerous. Savage and lost, they are compelled to seek their creator. The havoc they wreak threatens those who search for Alex, including his father, Richard.
In the end, it will threaten the very existence of the wood itself and of its natural mythagos. Richard must quest repeatedly through Ryhope's hollowings in an attempt to bring his son to safety and quiet the monsters Alex has created.
There his dreams continue to populate the wood with "mythagos", warped, dangerous hero figures, threatening all those who come in search of the boy.