The Mummy Imhotep needs the Manacle of Osiris to fulfill his quest to rule all mankind, but it's stuck on Alex's wrist, and only the Lost Scrolls of Thebes can remove it without destroying its power.
A clue about the Scrolls in the diary of Alexander the Great takes the O'Connells into the Egyptian desert, where they encounter Imhotep, who is also searching for the same palace.
En route to Australia, the heroes crash-land on a small tropical island, summoning a long-dormant lava creature that pushes the local volcano toward eruption.
In an effort to locate the Scrolls, Weasler and Imhotep kidnap Albert Einstein, and it's up to our heroes to save the genius before he shares any valuable information.
A vision takes the family to a mountaintop in Peru, where they meet the legendary Cloud People and the Native American spirit that protects the area from outsiders.
While in China, Alex befriends the young emperor of the Forbidden City, who promises to help find the Lost Scrolls - but instead accidentally unleashes a demon dragon.
The search is on for the three pieces of the Puzzle of Horus, which may lead the O'Connells to the Scrolls, but first they must battle Imhotep, Weasler and a giant sandworm.