The Lascaux Nightmare - kindle ebook by Robert A. Taylor

In 1941, 4 young boys from the village of Montignac, France uncovered
a prehistoric cave system that bore the artwork of generations of cave
dwellers. The elders of the village discouraged them from talking
about it with the outside world; if it hadn't been for the Nazi
occupation, no one would have known the paintings were even there. But
the Nazis thought that it made good press, and so the caves were
opened up.

Unfortunately for the outside world, the elders of Montignac were
right; and a generation later, if what was in the cave cannot be
stopped, the world will pay the price.