In the remote mountains of Croatia, an archaeologist makes a strange discovery: a subterranean Catholic chapel, hidden for centuries, holds the bones of a Neanderthal woman. In the same cavern system, elaborate primitive paintings tell the story of an immense battle between tribes of Neanderthals and monstrous shadowy figures. It isn’t long before the investigative team is attacked, while a bloody assault is made upon a primate research center outside of Atlanta. How are these events connected? Who is behind these attacks? The search for the truth will take Commander Gray Pierce of Sigma Force 50,000 years into the past.