Magic is fading from the Wild Wood. To renew it, goblins must perform an ancient ritual involving the rarest of their kind--a newborn changeling. But when the night arrives to trade a human baby for a goblin one, something goes terribly wrong. After laying the changeling in a human infant's crib, the goblin Kull is briefly distracted. By the time he turns back, the changeling has already perfectly mimicked the human child. Too perfectly: Kull cannot tell them apart, so he leaves both babies behind.
Tinn and Cole are raised as human twins, neither knowing what secrets may be buried deep inside one of them. When they are thirteen years old, a mysterious message arrives, calling the brothers to be heroes and protectors of magic. The boys must leave their sleepy town and risk their lives in the Wild Wood, journeying through the Deep Dark to reach the goblin horde and uncover who they truly are.