The Legend of Zelda: Majora's Mask (Zelda, #3)

After sealing Ganondorf in the Sacred Realm, Link returns to the time when he was a boy. Peace has returned to Hyrule, but his old friend Navi is missing. While wandering the forest in search of Navi, he meets Skull Kid, who is wearing Majora's Mask, an artifact said to grant your wishes. The mischievous Skull Kid steals the Ocarina of Time from Link and turns Link into a Deku Nut!