How do you fight fire without fire? When a freak storm uncovers the entrance to a mysterious underground chamber, Ivy and Martin expect to find treasure. But what they discover is even more valuable: a barrow full of sleeping spriggans, magically preserved for centuries. With the vengeful piskey queen Betony determined to capture Ivy and her followers, the secret hideaway could be key to both their peoples' survival. But the piskeys and spriggans...