Critical Difference is the story of a Colonial Survey Officer named Massey assigned to a barren, frozen planet to check and approve colony installations. He discovers that this world's temperature is gradually getting colder. Eventually, the declining temperature will make the colony uninhabitable. The colony receives a coded message that the same thing is happening to their home world. The colonists rely on Massey to find a solution.

Murray Leinster was the pen name of William Fitzgerald Jenkins, an American writer of genre fiction, particularly science fiction. He wrote and published more than 1,500 short stories and articles, 14 movie scripts, and hundreds of radio scripts and television plays.