The abominable snowman... The Yeti. For centuries his presence has been a speculation, but now his existence may be a reality. High in the Himalayas a specimen has been found and he's been sent back to the United States for research. Leading the investigation is noted anthropologist Doctor Claire Collier, who has been studying the controversy of the Yeti for years. The autopsy reveals that the extraordinary creature, whose ancestors date back perhaps millions of years, underwent some sort of cranial surgery prior to its death. How is the mystery to be solved, an expedition is the only way to find the answers. Collier teams up with Mat Connor, her former student and famous writer, Rondo Montana, an ex-big game hunter, and Kathleen Reidel, another one of Collier's former students and the guide for their journey. After several days travel, the team is surprised by an avalanche. The ground caves is dropping them into and ice caverns hundred of feet beneath the ice. The four explorers find a way out of the cavern and, surprisingly, into a warm and lush isolated valley inhabited by unusual primevals species. An occasional heat-emanating metal dome can be seen emerging from the soil. The aberration in the environment is obviously the work of some highly intelligent lifeform, which the researchers dare to find. Their suspicions are justified when the team find a remote cave with a hydroelectric system hidden inside, as well as the remains of an abandoned space ship. The explorers are suddenly captured by the strange beings - half reptile, half man - brought about by years of mutation. The creatures have a deadly plans for the humans... unless they can find a way out.
