Cressida Cowell, author of How to Train Your Dragon, brings us the next thrilling installment in the internationally bestselling Wizards of Once series! Xar and Wish are heroes with a huge task ahead--confronting the Nuckalavee is not for the faint hearted. But with Magic and Iron together, they might just have a chance of saving their beloved homes from those who seek to destroy everything they hold dear. The third electrifying book in The Wizards of Once series fizzes with magic and introduces us to a host of glorious new characters: bears and piskies and magical pins and needles to name but a few. Beloved, bestselling author Cressida Cowell once again brings her trademark wit and stunning combination of action, adventure, humor, and incredible artwork to this epic new adventure, sure to transport and enchant readers. Stunningly written, magnificent in scope, hilarious and thrilling, Knock Three Times immerses you in a world you won't ever wish to leave.