Jack Furness, mountaineer, is scaling one of the highest peaks in Nepal when he slips and falls into a crevasse - where a fossilised fragment of skull has lodged in the ice. Intrigued, he delivers the fossil as a challenge to his former girlfriend, a young palaeoanthropologist at the University of California. She is transfixed; the skull defies classification, but appears to be a rare example of an early hominid, a form of ape-man whom she names Esau. Jack and Stella set off on an expedition to track the hominid form, despite worsening political situation and the threat of nuclear war on the Indian subcontinent. They believe they may come across other skeletons, or even living examples of this strange creature, the fabled yeti. What they discover is a terrifying new breed of ape-man that has serious implications for science and chilling consequences for Jack and Stella. The tension escalates as they discover that there is a mole on the expedition whose mission is in direct conflict with their own.