Four stories in the collection feature the character of Wendell Urth, who is a leading extra-terrologist (an expert on alien worlds and life originating on them).
Urth is eccentric in that he has a phobia of all mechanical forms of transport (an exaggeration of Asimov's own aversion to flying).
Urth appears in the stories when he is consulted by an agent of the Terrestrial Bureau of Investigation, H. Seton Davenport, in cases which have him baffled – a parallel with the way in which Inspector Lestrade consults Sherlock Holmes.
In a fifth story in the collection, "The Dust of Death", Asimov shows Davenport a generosity that Conan Doyle never extended to Lestrade in demonstrating the former's ability to solve a case for himself without Urth's assistance.
This article about a collection of mystery short stories published in the 1960s is a stub.