In this third book of the saga: The Emperor Shangri-La died trying to attack the Earth; the Empress-his twin sister-died trying to attack Tom Swift. Now, it seems the very Moon on which they built their Shangri-La colony of slaves is on the brink of being attacked by the ground under their feet. Harlan Ames, former Swift Enterprises Chief of Security has been the Administrator of the now free colony but is getting anxious to take his twin children back to Earth. Their safety may depend on it; their mother was the much hated Empress But, something bad is happening inside the Moon. He hopes his old boss can figure things out before it is too late. In the meantime, he leaves his children in the care of Lola "Grandma" Reyes at the lunar colony while he heads out to see if there is anything to discover at the former "Master's" ruined fortress in the Philippines. It is a race against time to see if clues can be found to help avoid a catastrophe.