Styx

Thousands of years ago, mankind make the gigantic leap from hulking Neanderthal to lordly Cro-Magnon. The explanation for that evolutionary step - the missing link - has never been found...until now. An earthquake rocks Yugoslavia, uncovering the ghostly subterranean world of the awesome Subrano Cave. Its amazing paintings and fossils chronicle the existence of an ancient, mysterious race. As the dawn of man is slowly pieced together by an international investigative team, they discover that this unusual tribe disappeared deep into the earth, leaving a trail of paintings along the banks of an underground river. When another earthquake seals the cave for all time, the trapped survivors who have been studying the cave paintings have no choice. There is only one possible way out - ad that is to follow a path taken 40,000 years ago. They must ride the underground river Styx, all the way to Hell...