The Blue Ghost Mystery

This is a pretty straight forward mystery.
It was nice to see Jan and Barbie involved although they didn't contribute enough to the solution.
The science/engineering stuff was weaker than most of the books, but there was some good geology.
The foxhole radio they make was pretty cool to read about in the 1960s but now, I mostly wondered where somebody would get rusty razor blades.

At the end, when the bad guy is confessing, I couldn't help thinking he was going to say
“And I would have gotten away with
it if it hadn't of been for you meddling kids!”