The twins journey into the Underground, discovering that they are not only elves, but “royals” and that their bloodline is in danger of extinction at the hands of their parents' murderer, Vyra Vaun. Living in a skyscraper tree called Arbor Castle, the twins seek to join the Warriors, a group of elves who fight to defend the kingdom and to stop Vyra and her malevolent followers.
But Autumn soon becomes distracted, locked in an elfin love triangle with forbidden, golden-haired Avery and brooding, green-eyed Victor, who has a dark secret. She realizes she must make a choice. Little does she know her decision could very well mean the difference between life and death for all of the Underground.