Richard Callum was a former author who owned and operated a pub called the White Lion on a small British island. He was married to Frankie Callum but had apparently had an affair in the past with Patricia Wells. Although Richard often professed he was a man of no imagination, theories of an air force radio operator named Pearce that a bizarre heatwave affecting the Island were the cause of aliens began to worry him and make him increasingly suspicious of the White Lion's sole guest, Harsen. When Patricia said she thought she saw a spacecraft land nearby, Richard phoned Vernon Stone, a science fiction author he knew, and Stone agreed with him about the possibility of an alien invasion.
Along with Stone, Frankie and Patricia, Richard went outside to try and see where Pat had said she'd seen the spaceship land. Instead they only saw Harsen (who Richard had seen leave the house prior), and they all began to suspect he was in league with the aliens. But when Richard confronted Harsen, the scientist revealed he had been collecting evidence to give the government proof of the impending invasion, and from then on the two men worked together. Following two failed attempts to reach the Island's radio station by road which cost the lives of both Harsen and Stone, Richard took Frankie and Pat in his roadster and attempted to reach the station by driving off-road, which resulted in the car becoming mired in hot sand.
Despite meeting up with Pearce, Sir James Murray and Gieves, who were headed to the radio station anyway, after their Land Rover broke down due to the heat Richard eventually decided that the aliens were winning and that it would be best for them all to just go home. Go home Richard and Frankie did, to wait out the inevitable in the White Lion with their neighbor Brenda and her children, the local vicar, and Lanky Robert who had claimed to have seen hundreds of the aliens in some caves nearby. Ultimately, the intense heat generated by the aliens' radio beam heat ray started brush fires which turned the aliens' own weapon against them, killing the creatures and saving Richard, his wife, and their neighbors.