The Rivals of Sherlock Holmes Set Two comprises the second season, originally broadcast in 1973. Many of the stories are set outside of England and were republished in Greene's anthology, Cosmopolitan Crime: The Foreign Rivals of Sherlock Holmes (1971). While the tales themselves tend to be lightweight entertainment, originally published in pulp magazines or collections, the "back stories" about their authors and cultural context is often fascinating and surprising.
"The Mysterious Death on the Underground Railway" is based on the story by Baroness Emma Orczy, a spectacularly successful Hungarian-born woman writer who is most famous for authoring the Scarlet Pimpernel novels. Published in Orczy's 1909 collection The Old Man in the Corner, this tale features spunky female journalist Polly Burton (Judy Geeson), who assists her uncle, a barrister, and constantly agitates for an opportunity to cover "serious" stories. A woman is found dead on a train. Polly becomes involved in the mystery as the woman is identified by a seemingly grief-struck husband and sister, and Polly's uncle prosecutes a male friend for her murder. Polly is no detective, however—another character solves the crime while Polly somewhat breathlessly follows along in hope of a scoop. Judy Geeson also appears as Caroline Penvenen Enys in the 1977 BBC series Poldark (also just released on DVD by Acorn Media).
One of the most fascinating background details of this episode involves the eatery where several long scenes take place: a recreation of one of the Aerated Bread Company "tea shops" that were established in the 1860s. These "tea shops" were among the few places where an unescorted Victorian woman could enjoy a public meal with safety and propriety, and the ABC was involved in several issues related to women's rights and health.
"Five Hundred Carats" is based on a story by George Griffith, a very popular science fiction author whose writing pioneered the style currently known as steampunk. Griffith wrote from a deeply felt socialist-utopian philosophy, which may be why he never became as popular in the United States as some of his contemporaries. This outlook shows strongly in the character of Inspector Lipinsky (Barry Keegan) of South Africa, a "former laborer" who has risen through the ranks by his own integrity and dedication and who suffers the disdain of the "gentlemen" of the colonial elite. A luxurious private club even complains when one of the De Beers diamond magnates invites Lipinsky into the club as a guest. The episode is structured as a flashback from the grisly murder that opens it. Inspector Lipinsky has to figure out how the largest perfect diamond ever discovered disappears from its secure and guarded storage room at the De Beers headquarters. A supporting role is played by Richard Morant, who appears as Dr. Dwight Enys in the series Poldark.