sentences:  This story was Hayles' first submission to Doctor Who.The story focused the Doctor, Ian, Barbara, Vicki landing the TARDIS on the planet Numir, which its sun was extinguished, and encounter the surface dwelling ‘light people’ and the subterranean ‘shadow people’.The story was rejected by story editor Dennis Spooner on February 8, 1965, because the story was too similar to Malcolm Hulke’s "The Hidden Planet".