41,000 years ago the world was changing, the glaciers and grasslands expanding, the forests contracting. Eagle, a Neanderthal, discovers that his people are being systematically slaughtered by a monster beyond his darkest imaginings. Long Cloud is a Cro-Magnon woman abducted as an intended mate to bear children for a would-be tyrant, a werewolf and an egomaniacal castaway who seeks to build a cult with himself at the center, his immediate goal the complete annihilation of the remaining Neanderthals. Rejecting his mad vision, Long Cloud escapes his clutches but finds that she has no safe haven among her own people.
Struggling to survive in a frigid, unforgiving world of woolly mammoths, giant rhinos, and savage hyenas, the two learn that sometimes The Other can become your closest friend. As the systematic slaughter of the Neanderthals spreads and with no one to turn to but each other, Eagle and Long Cloud overcome their learned preconceptions, language barriers, and disparate world views to become unlikely allies in their efforts to end a monster's murderous campaign.