In the 4th book of the saga, everything appears to be going smoothly on the Moon as the forthcoming Lunar Resort is taking shape, but behind the scenes there are troubles with at least one attraction planned that is taking a lot of Tom Swift's time.Meanwhile, Harlan Ames is trying to find closure over the entire The Masters episode and some gems left behind in their former fortress. He tracks down the probable source and, along with a civilian archeological team, heads back to the Himalayas, but he must first dispose of some very disturbing evidence!To make matters worse, a very ill man who holds Tom responsible for a family tragedy is out to kill the inventor and finds a way to get to the Moon, become one of the construction crew, and lies in wait for the opportunity to kill.