Twins Nick and Sam (Samantha?) are spending the summer on an archaeological dig being supervised by their parents, at a remote site which is proving to hold a large number of Triceratops fossils. Nick and Sam aren’t too interested in this, oddly, but they do enjoy camp life, and exploring. On a walk they discover a Caesar cypher wheel (similar to the one pictured above) carved into a cliff. One of the research volunteers, Becca, shows them how it works, and the twins begin a new search for something written in code that they can use the wheel to decipher. Before long they have found several code fragments, and eventually an entire book in code. Meanwhile, they are being threatened by a mysterious figure who seems to want what they’ve found. Becca and some friends from the nearby small town of Oak Creek seem to know more about the codes and other odd secrets that might lead to a lost underground town, if they can figure out where it is.
This was a fun read, but it has one major problem: Nick and Sam have things too easy. There is little conflict here, they go from one triumph or discovery to another with not much effort. They always get things right, or are helped at just the opportune moment. Yes, there is a mysterious threat, but it doesn’t bother them too much, and is eventually dealt with off-camera by others. I’m all for fun adventure stories, but when the protagonists have everything they want practically handed to them, it makes for a dull story.