. . . and a new magical journey unfolds when the tree house lands in Mongolia, Jack and Annie can hear the drum beat of horses hoofs. The little horses of Mongolia are returning from near extinction and the kids get to meet the people who take care of them. But the horses are still in danger with wolves nearby. . . Can Jack and Annie protect the last of the little horses? Merlin Missions: More challenging adventures for the experienced reader Fact Trackers: Nonfiction companions to your favorite Magic Tree House adventures Graphic Novels: Relive the original adventures brought to life with art by Kelly & Nichole Matthews If you're looking for Merlin Mission #39: , it was renumbered as Merlin Mission #11 when the series was rebranded in 2017.