Fenton Hardy is trying to find out who is out to sabotage a new military radar installation. At the same time the boys are on the trail of a missing college professor. It seems the further the boys travel in following the missing professor, the more suspicious characters they discover. Some people they encounter who appear suspicious may not be, and others who appear to be uninvolved may be. How will the boys learn where the missing professor is located?
During the boys investigation they come across a huge complex of caves. During their stay in the cavern the boys have their stuff stolen, and are threatened. What could be so important that someone would want to chase the Hardy Boys away?
I have been a big fan of the Hardy Boys since I was a child. However, I found this particular book to be less enjoyable than some of the other books. The main reason is that the author appeared to know little about the military and military construction, and his description of the sabotage at the radar site would have involved the FBI and much heavier security, among other details. However, if you can get over the minor annoyances, the basic story has some interesting twists.
As I noted in my review of Hardy Boys #6, "The Shore Road Mystery," the author seemed to have a fixation on caves. The five previous books in the series had caves and the next story has a cave. I guess caves are just very mysterious places along with being great criminal hangouts.
Though the Hardy Boys series is written in a relatively archaic fashion, as reading material for an increasingly younger audience they are excellent. The stories were once recommended for children ages 10 to 14. As children are exposed to more violence and seem to require greater levels of stimulation, the recommended age range has move to 9 to 12. I think any child capable of reading some of the challenging words in these books will enjoy them, regardless of how tame most of the action may be. Once a child has reached age 12 or so the stories may be of less interest, but given the combination of mystery and action, these books remain good safe choices for parents who want to know what their children are reading.