* AdaptationDisplacement: The TV series is much more famous than the series of novels it was originally based on. It's also markedly different from the original series of novels. In the books, Murdoch is much more of a DeadpanSnarker and is outright contemptuous of Brackenreid, and solves his cases through legwork and talking to people rather than any form of science. Inspector Brackenreid is depicted as an incompetent drunk who's also bigoted against the Catholic Murdoch. George Crabtree is described as having a large build and is a married father of five.
* CallBack: Not within the show, but within ''Frankie Drake Mysteries'', which exists in the same universe. George Crabtree appears in a first-season episode set in the early 1920s, where it's revealed that the investments he made in "Who Killed the Electric Carriage?" [[spoiler:have made him [[EarnYourHappyEnding wealthy enough to retire from the police force while still very young]]]].
* CompleteMonster: [[FauxAffablyEvil James Gillies]] is Detective William Murdoch's ArchEnemy and one of the most dangerous men he's ever met. Initially coming into conflict with Murdoch after he murdered his professor as part of a way to [[ForScience test a theory of Applied Physics]], Gillies was defeated when Murdoch tricked his weak-willed partner, Robert into turning on him. After escaping the noose by bribing a dying man into taking his place, Gillies murders Robert by sawing his head off while he's still alive. He then initiates a [[CriminalMindGames twisted mind game]] with Murdoch that culminates in him [[BuriedAlive burying Julia alive]], with Murdoch only narrowly getting there in time to save her. Unfortunately, Gillies escapes and one year later [[FrameUp frames Julia]] for the murder of her husband, all as part of a plan to lure Murdoch into a SadisticChoice of either saving his own life or that of Julia. Fortunately Murdoch is able to alert his fellow officers, who arrive in time to save him before the [[DeadlyGas poisonous gas]] floods the room. Afterwards he arranged for several criminals to break onto the train transporting him into prison, causing chaos which he used to try to escape, all the while taunting both Murdoch and Julia that they "owe him" for killing Julia's husband and allowing them to be together. Finally he makes a final play for revenge on Murdoch that climaxed in him endangering a child Murdoch had come to care for. Sadistic and defined by pettiness, James Gillies is the worst that Detective Murdoch has ever faced.
* EnsembleDarkhorse: There are many fans who are quite fond of Henry Higgins, and would very much like to see his character become part of the main cast. He and Constable Jackson have both been making more appearances since the beginning of season 8, often together with Crabtree, so it seems the writers have listened to some extent.
* FoeYay: Some fangirls began to ship Murdoch and James Gillies together after [[spoiler: the latter kisses the former on the mouth for a full three seconds in "Midnight Train to Kingston."]]
* HolyShitQuotient: Viewers all across the board were completely stunned when [[spoiler:Gillies kisses Murdoch rather passionately in "Midnight Train to Kingston"]]; ''no one'' saw that coming!
** Between Crabtree and one-off character Nuniq, including a goodbye kiss (on the cheek).
** The Season 11 premier has a moment between Murdoch and [[spoiler:George, when he learns George survived the ambush after he was originally reported killed. Lampshaded with amusement by Brackenreid and Julia, when they both note Murdoch was more overjoyed to see ''George'' than he was to see them. Yes, even moreso than his ''wife''.]]
* TheWoobie: Whenever Murdoch breaks down and is NotSoStoic, especially when Julia told him about [[spoiler:her abortion and that it left her barren]] and implied that she wanted to break up their relationship.
* ValuesDissonance: All over the place due to the setting, as the series largely averts PoliticallyCorrectHistory:
** Casual racism towards blacks, Jews, the Irish, Chinese, etc., a sharp divide between social classes, sexism, the treatment of homosexuals, and religious intolerance are openly on display. More progressive characters do call attention to the unfairness of it, but other characters are allowed their prejudices without losing sympathy, and these attitudes are presented as simply how the world is.
** Heroin, opium, cocaine, and other drugs are all used medicinally with nary a blink.
** Eugenics is still considered a serious science, despite having been discredited. What makes it this as well of ScienceMarchesOn is its close ties to concepts of racial and class superiority; one murder was committed by a man whose fiancée's father disapproved of their marriage because of his "lesser" pedigree. [[spoiler:Ironically, the victim reconsidered and was even going to leave the Eugenics Society.]]
* WhatAnIdiot: It's understandable that James Pendrick doesn't think much of Thomas Edison, given that the latter has been hounding him on suspicion that he's violating Edison's film technology patents. However, when you're an aspiring film director, it's probably not a good idea to turn down a job offer from the man who owns just about every movie screen in the United States, much less call him a "scoundrel" to his face.