* FanPreferredCouple: Despite a 27-year age difference between the characters, 73 percent of ''Foyle’s War'' related fanfics found on Platform/FanFictionDotNet as of the beginning of 2012 romantically pair Christopher Foyle and his driver Samantha Stewart. This continues to be more popular even after Sam gets married to Adam Wainwright.
* GeniusBonus: Or at least a bonus for the musically literate. A piano piece that is heard several times in "Elise", associated with the episode's title character, is not identified beyond a remark that Music/LudwigVanBeethoven is perhaps not a tactful choice given the war; it's Beethoven's Bagatelle No. 25 in A minor, "For Elise".
* HarsherInHindsight: The death of poor Lucy Smith in "Eagle Day". In the episode, it's generally regarded as an innocent young girl seduced by an older man, in over her head, [[spoiler: who commits suicide over her resulting pregnancy,]] which is subsequently covered up because the man concerned is a key part of an experimental program. Which doesn't stop Foyle from telling the man's superior [[TheReasonYouSuckSpeech "What he did to Lucy Smith might not have been strictly criminal, perhaps, but it was immoral, improper, and downright disgusting."]] When re-watched in the wake of the Harvey Weinstein scandal and the #Metoo campaign, it comes across as something far nastier: Major Graham using his position as her superior officer to intimidate and manipulate Lucy into becoming his mistress, partly by implying that providing sexual services to him was part of her job for morale purposes. (On the Wikipedia page, it's stated outright to be sexual assault.) Even worse, as they were both staff members of an experimental scientific program, the whole mess came under the Official Secrets Act, giving Lucy no recourse to the usual chain of command which should have protected her. (whether it would have, given the sexist attitudes of the time, is another discussion altogether) [[spoiler: It's no wonder Lucy's father kills Major Graham, and has no regrets whatsoever about doing so.]]
* NightmareFuel:
** The first episode, "The German Woman": the victim is nearly decapitated by an invisible length of piano wire while out riding. The sight of the riderless horse coming back to the manor, its (white) flanks splashed with blood obviously not its own, is enough for one of the maids to start screaming.
** In "The White Feather", British fascist leader Guy Spencer has gathered prominent supporters at the eponymous hotel to give a speech. During the pre-speech cocktail party, the members are sagely agreeing how many British newspapers and institutions are being controlled by Jews, and one of them is doing a caricatured impression of a Jewish businessman that has his female companions in stitches. Then the piano player sings a jaunty music-hall style number, the chorus of which is "Hitler's got 'em on the run in Germany… why can’t the Jews just stay out" which has all the members laughing and singing along. It is uncertain how much anyone else in Britain knows of the full horror of what the Nazis are doing to the Jews in Europe, but these people give the clear impression that they not only know, but they'd happily pull up chairs outside the gates of Auschwitz and [[PassthePopcorn pass the popcorn]].
** "Eagle Day" (see HarsherInHindsight above): Besides the sexual assault and subsequent tragedy that kick-starts the mystery, more than one character strongly hint that one of the major hazards of being a servicewoman is fighting off male colleagues who think that the ladies should be providing other kinds of service(read: sexual) as well.
** "Fifty Ships": The MoodWhiplash that occurs in the opening scene: Sam is slumbering on her bunk when German planes are heard overhead. Her roommate says they're all evacuating to the basement, but Sam mumbles, "can't we just ask Jerry to come back later?" Seconds later a bomb hits, killing the roommate and barely missing Sam.
** "War Games": Simon Walker's shrine to Hitler in his father's basement; his father is illegally doing business with the Nazis, but he's OnlyInItForTheMoney, and even he is disturbed by the depth of his son's fanaticism.
** "Among the Few": a black marketeer is killed when the truck he's driving, laden with illegal gasoline, explodes in flames. Foyle glances through the driver's side window, and the camera shows just enough of what's left of the man to make the audience profoundly grateful that they can't see the rest.
** "The French Drop": a man dies of an apparent suicide after pressing a grenade to his head. Not much of the corpse is shown, but Milner's description is enough to paint the picture.
** The effects of anthrax, in both its deliberate testing on livestock and its accidental spread to humans.
** Also the [[spoiler:coffin factory]].
* RetroactiveRecognition: The show contains a near-hilarious amount of young British actors who went on to make Hollywood's A-list, particularly Creator/JamesMcAvoy (who is best known for portraying the younger Professor Charles Xavier in the ''Film/XMenFilmSeries''), Creator/RosamundPike and Creator/EmilyBlunt. Also featured are the fresh young faces of Creator/DavidTennant, Creator/SophiaMyles and Creator/TobiasMenzies.
** The show has also featured older, already well-respected actors who have since become more familiar to general audiences through higher-profile roles--most notably Creator/CharlesDance and Creator/PeterCapaldi.
** On the international front, Lars Eidinger as Karl Strasser will be easily noticed by any fans of the later smash it ''Series/BabylonBerlin.''
* SpecialEffectsFailure: When Grace Philips' factory station explodes in "Bleak Midwinter", it's clear that there's no one sitting there.
* TheWoobie:
** Susan Gascogine. Her father, a judge, threatens her boyfriend with imprisonment on false charges because he's not posh. She takes in a Blitz evacuee because he seemed unwanted, but her parents hate him for having lower-class manners and she can't connect with him as she'd hoped to. Her father's life is threatened and the young boy dies. When she breaks down in front of Milner, her father walks in and throws him out, [[spoiler:and he's soon shot dead. Finally, her own mother confesses to murdering her father, because he had been the one to kill the child.]]
** Mrs. Graham in "Eagle Day." She's an innocent woman who has no idea that her husband is unfaithful, much less that he's driven a young woman to suicide. She's just sitting with him, having a quiet evening at home and talking about a concert they'd both been to [[spoiler:when someone knocks at the door and stabs him dead]].
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