Bowen Tyler and his crew find themselves marooned in a nightmare world of mighty dinosaurs and bestial apemen who kill on sight. This is the lost continent of Caspak, a hot, dark and mysterious prehistoric world located somewhere in the icy waters of the Antarctic. Their only hope of rescue is a note in a bottle flung into the sea. The survivors persist and penetrate the heart of Caspak to find the incredible secret that claws, fangs and spears have guarded since the beginning of time.