A spaceship carrying illegally-mined radioactive ores from the asteroids is all-but destroyed by an accident, and Wendell Urth is consulted to try to determine the location of the asteroid the ores came from. All he has to guide him are the last words of the non-human creature left dying aboard.
Like many of Asimov’s mystery stories—including the first Wendell Urth mystery, “The Singing Bell”—this is a puzzle story, a brain-teaser. The characters and plot are entirely secondary to the problem presented and solved. Here only two of the characters, Urth himself and the pool pathetic “silicony” are worth mentioning, and the latter is callously killed off so as to leave mysterious dying words (a flaw Asimov himself points out in Asimov’s Mysteries). So although this is a good enough story, it is not top-notch.