"The Adventure of Colonel Nivin's Memoirs" establishes its conflicts in the recent-as-of-the-setting vicissitudes of World War Two, as well as the still-building Cold War. When the episode aired, more recent history involved Watergate and the Vietnam War. The episode, consciously or not, injects some of the issues of 1975 into its 1947 setting.
Now with very few exceptions, cop shows and detective shows tend to draw on an older, more conservative audience. That being the case, you might expect a prime time whodunit examining Watergate-era betrayals in a post-WW2 setting to be muddled in some places, simplistic in others. Unfortunately you'd be right, which is why this isn't one of the stronger stories. Has its charms, though.
A secret agent with His Majesty's Secret Service has written a not-quite-tell-all memoir about his service, notably spilling the beans on people he knows of who fell short in some way during the war years. A sometime ladyfriend of Ellery's named Jenny O'Brien is working with publicity with the author, presumably for the publisher. He pressures her to accompany him to the book release cocktail party that night, in a way that's meant to seem charming but is really just heavy handed. (Inappropriate even for a seventies facsimile of the forties. If nothing else this is a show where sexual harassers get theirs.) She ropes Ellery into attending as well as sort of a buffer. Then she goes to see the Colonel at his men's club and finds him dead at his desk.
By what do I mean "not-quite-tell-all"? Well, the Colonel seems to have provided details in his book, but hasn't named names. The implication seems to be that he'll get to the names in a sequel, and that the prospect of being further shamed is what motivated the killer. It makes the book he's currently flogging seem like a thin affair, though, especially for one that we're told sold out its first printing in a day. Another problem with this setup is that while the subjects of the book are unnamed, two of them manage to out themselves by leaving a copy out with the pages that slime them bookmarked. D'oh!
Ellery Queen, throughout its single season, was able to attract an impressive cast of guest stars. This episode is no exception. Oregonian actress Gretchen Corbett is a lot of fun as Jenny O'Brien, and has good chemistry with Jim Hutton. Jenny and Ellery's flaws are complementary: she's impulsive and demanding while he's forgetful and has glaring social lapses. If anyone could have been a regular love interest or just partner on this show, Corbett had the most potential. They didn't go that way, and maybe her similar duties on Rockford Files would have made the scheduling awkward.
Also appearing are craggy character actor Robert Loggia and Rene Auberjonois, then best known as part of Robert Altman's stock company. Auberjonois's French photographer is living a pretty convincing bohemian life. When his interrogation is interrupted by his fiancee there's a definite implication of "if it makes you feel better to call her that."
As for Pernell Roberts, he does what he can with a rather incoherent masquerade of a character. Mild spoilers follow. Roberts first appears as a turban-wearing Indian doorman at the men's club. (You read that right.) Fingerprints reveal that he's actually a petty criminal trying to go straight. But further investigations show that the criminal has been dead for two years, and Roberts' character is an OSS man working deep cover. Left unexplained is why he needed a second alias to pose as a doorman, or who thought it was a good idea for him to go the brownface root when the English members of the club might have met some real Indians.
Further, the spy shop stuff just doesn't pan out. There are hints that everyone in the story is under some kind of surveillance, with cars surreptitiously following other cars and the Queen apartment getting tossed. But it just dissipates with no payoff.
I don't want to be too down here. The Ellery/Richard Queen/Velie interactions are very good, as is Ellery's detection. It just doesn't hold up to scrutiny as well as some of the others.