In their magic treehouse, Jack and Annie are again transported to King Arthur's realm, where invisible beings, giant ravens, and mistaken magic spells have a duke's castle in an uproar on Halloween night.

Jack and Annie are joined by Teddy and Kathleen as they travel to the snowy Land-Behind-the-Clouds, where they search for the eye of the Ice Wizard and attempt to help Merlin and Morgan.

The magic tree house carries Jack and Annie to New York City in 1938 on a mission to rescue the last unicorn.

When Merlin is weighed down by sorrows, Jack and Annie travel back to feudal Japan to learn one of the four secrets of happiness.

When eight-year-old Jack and his seven-year-old sister, Annie, join a group of nineteenth-century explorers aboard the H.M.S. Challenger, they learn about the ocean, solve the mystery of its fabled sea monster, and gain compassion for their fellow creatures.

Merlin the magician will not eat or sleep or speak to anyone. The enchantress Morgan asks young Jack and Annie of Frog Creek, Pennsylvania for help. Jack and Annie know they have to search for one of the four secrets of happiness to help Merlin the magician find joy in his life again. And so they head off in the magic tree house for Florence, Italy, in the early 1500s, then to a misty island in the middle of nowhere, then to the continent of Antarctica....

Jack and Annie travel to Vienna, Austria, in 1762 where they meet the young Wolfgang Amadeus Mozart and his sister and help save the budding genius' life.

Jack and Annie travel back to nineteenth-century Ireland to inspire a young Augusta Gregory to share her love of Irish legends and folktales with the world.

The magic tree house whisks Jack and Annie to India during the Mogul Empire in the 1600s to search for an emerald needed to break a magic spell.