In this adventure, Merlin the Magician sends Jack and Annie on a quest to find the “Secret of Happiness.” To find it, the Magic Tree House whisks them back in time to 1600s Japan, specifically the city of Edo (now Tokyo). There, they meet one of the world’s greatest poets, Basho. However, their mission becomes dangerous when they are mistaken for spies by the Shogun’s samurai. Jack and Annie must navigate the ancient city, endure a terrifying fire, and learn the true meaning of happiness through Basho’s wisdom and a bit of “merlin” magic before they can return home.