When the crew figure this out, they set up the means to destroy the mist. The reference to M33 in the title of the story is apparently an error: the galaxy described is the Andromeda Galaxy (M31), rather than the Triangulum Galaxy (M33). The latter is in the constellation Triangulum rather than in that of Andromeda. "The Expendables" (Worlds of If, September 1963) "Heir Unapparent" (as "Heir Apparent" in Astounding Science Fiction, June 1945). In this story the emperor of the world, who seized control 50 years ago with the aid of a super-weapon that he designed, is dying. He has been poisoned and has 48 hours to live. With his remaining time he has to find out who did it, stop a military take-over and keep his heir apparent (his granddaughter) from taking over. "The Weapon Shop" (Astounding Science Fiction, December 1942) 1971 short story collections Fiction set in the Andromeda Galaxy Short story collections by A. E. van Vogt 1970s science fiction works