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

Jack and Annie travel to a monastery in the Swiss Alps where, with the help of St. Bernard dogs and magic, they seek the second of four special objects necessary to break the spell on the wizard Merlin's beloved penguin, Penny.

Jack and Annie visit the Paris World's Fair of 1889 in an effort to protect four scientific pioneers from an evil sorcerer.

"The magic tree house has taken Jack and Annie back in time to England in 1944. England is fighting for its life in World War II. Before long, Jack and Annie find themselves parachuting into Normandy, France, behind enemy lines. The date is June 5. Will the brave brother and sister team be able to make a difference during one of the darkest times in history?"--Provided by publisher.

Magically transported to southwest China to find the final object needed to break the spell on the wizard Merlin's beloved penguin, Jack and Annie take a side trip to the world's largest giant panda reserve.

Jack and Annie travel in their Magic Tree House back to a Hawaiian island of long ago where they make friends, learn how to surf, and encounter a tsunami.

Jack and Annie join Merlin on a magical mission to King Arthur's castle at Camelot, a haunted castle, fight a giant sea serpent, and travel to the land of snow.

Stage fright on a summer night: The show must go on! That's what Jack and Annie learn when the Magic Tree House whisks them back to Elizabethan England. There they meet William Shakespeare who's having a hard time with some of the actors in his latest show. Are Jack and Annie ready to make a big entrance? Or will it be curtains for Shakespeare? Good morning, gorillas: Gentle giants or giant monsters? That's the question Jack and Annie have...

Dolphins at daybreak: Their magic tree house takes Jack and Annie deep into the sea, where they meet up with dolphins, sharks, and octopi as they search for the answer to an ancient riddle. Ghost town at sundown: Their magic tree house takes Jack and Annie back to the Wild West, where they experience excitement and danger and try to solve a riddle. Lions at lunchtime: The magic tree house takes Jack and Annie to Africa where they meet up with wonderful...

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....