A caveman from 250,000 years ago is accidentally brought to the future by a time-traveling biology expedition, after which he lives in an enclosed extinct species park for contemporary humans to visit. The park manager, Doyle, who has come to the park with his wife and children, is meanwhile facing both a career and family crisis. Then, an accident at the park’s control center traps Doyle’s family and the caveman in a thrilling prehistoric adventure...