A Navy expedition led by Commander Hal Roberts (Jock Mahoney, Tarzan Goes to India) is sent to explore a mysterious warm-water region shrouded in the ice of Antarctica. When a fierce storm drives them into a cloud bank, their helicopter is disabled. Descending through the heavy fog into a deep chasm, they encounter a hot, tropical landscape of prehistoric terror! Untouched by the Ice Age and the imprint of time and evolution, a 20th-century Mesozoic era awaits them, complete with ferocious dinosaurs and carnivorous plants. While trying to repair their chopper and forage for food, they discover they are not alone. The only female among them, journalist Margaret Hathaway (Shawn Smith, World Without End), is captured by the sole survivor of a previous expedition. Driven to madness by isolation and the terrors of life in the primordial jungle, this desperate man may be their only hope for escape from The Land Unknown. Directed by cult filmmaker Virgil W. Vogel (The Mole People).