The Stones of Peril — James C. Work

City cops face prohibition bootleggers, gangster gamblers, and get complaints about this loud new "jazz" music. But up at Rocky Mountain National Park, Ranger McIntyre has nothing to do except eat breakfast, go fishing-and solve a couple of possible murders...

An amateur mountaineer is found hanging from his own rope on Flattop Mountain. Then a geologist studying stones on Flattop somehow ingested a poison plant. Both deaths could be accidental-except that a pair of odd-looking creatures has been seen on the mountain, creatures who appear to be adding new rocks to Flattop's ancient aboriginal stone circle.

Ranger McIntyre has a further complication. Her name is Vi Coteau and she's an FBI secretary in Denver, independent as an alley cat and drop-dead gorgeous. She wants the good ranger to teach her all about backcountry camping. Why not? McIntyre was planning to go into the wilderness anyway to look for the source of the strange stones being added to the medicine circle. If he took Vi with him, it would be an adventure... in more ways than a backcountry ranger might imagine.