Wrath of the Unicorn

On the open plains of Pleistocene Europe, a pair of male European cheetahs watch as their brother is chased down by an enormous and agitated Elasmotherium; provoked by the young cheetah's curiosity and ignorance as his kind are built for relatively small, swift prey like deer, horses and young bovines, not behemoths like the Elasmotherium or mammoths.
Setting: France, 800,000 B.C.