Henry is excited when his Uncle Jake builds him a tree house but worries that his dog Mudge will not be able to enjoy it with him.

Jack and Annie travel in their magic tree house to the land of the mystical selkies to seek a magical sword for Merlin.

"When Jack and Annie receive an invitation to spend Christmas Eve in Camelot--a magical place that exists only in myth and fantasy--they know they are in for their biggest adventure yet. What they don't know is that the invitation will send them on a quest to save Camelot. Can they succeed even though Camelot's greatest knights have failed?"--Amazon.com.

This time, meet famous explorer Leif Erikson and help save a narwhal! When the magic tree house whisks Jack and Annie to Greenland, they're not sure what time they've landed in, but they immediately know what their mission is: save a narwhal! Then, they meet a young hunter named Leif Erikson, and they ask for his help. But Leif has other ideas.

The magic tree house is back with a message from Morgan le Fay telling Jack and Annie to seek out "The Gray Ghost" and listen to her story, and immediately they are whisked away to Nepal where they meet Tenzin, a climber who has recently lost his family, and who takes them up the mountain to meet a snow leopard and renew himself.

Fifth-grader Winnie, with notes from her friends, writes of turning her treehouse into an embassy after her newly-divorced parents become unreasonable, where she is joined by nine others with complaints.