The Caves of Drach
 A multi-billionaire's grandson gets lost in the Caves of Drach in Majorca. The grandfather employs the team of astronauts (who are on holiday) to investigate. The expedition finds him in a huge and airy underground civilization peopled by practically immortal age-old humanoid beings who hail from the stars and took refuge underground when a Terran Ice-age threatened. The 'Cenobians' have a utopian civilization and avoid contact with the surface to keep it that way, and yet their advanced technology could bring an end to famine and disease.