The show revolves around Eliza Scarlet, played by Kate Phillips, as London's first female private investigator, and her lifelong friend in Scotland Yard, Inspector William "Duke" Wellington, played by Stuart Martin.
The series is in syndication in the United States on PBS's Masterpiece.
Miss Scarlet and the Duke contains examples of:
- Artistic License – History: Despite being set in the Victorian era, there are a lot of anachronisms. One of the most amusing is a reversal of the show's premise. In fact, in Victorian England, there were quite a number of female private detectives. By 1858, there was an entire profession of them opening up due to the Matrimonial Causes Act resulting in many job opportunities for female investigators (primarily of men for adultery). Ms. Scarlet investigating murders would have been strange but not the idea of a lady detective at all.
- Batman Gambit: In the end of series 2, Eliza is facing the first criminal she put away who is seeking revenge. While at held at gun point, she offers the man money to save her life. The man's greedy nature gets him to pick up the money, unaware she laced it with a paralytic poison. She had planned ahead with her sex worker ally what to do if she encountered the criminal and send him to Eliza's location.
- The Beard: A subplot in season 1 has Eliza's landlady Ms. Parker trying to marry off her son Rupert, first to Eliza herself, then eventually to another woman. Eliza learns during an investigation that Rupert is gay (both he and the Body of the Week have blue roses on display, a covert signal to other gay men at a time when male homosexuality was illegal), so she would have been his beard, as is the German gentlewoman he ultimately marries.
- Because You Were Nice to Me: In season 2, William is made to take the police commissioner's well-meaning but untalented son under his wing, and takes the role of mentor seriously despite his initial misgivings. Fitzroy ultimately saves William's job by organizing the detective squad to stand up to his father: they threaten a mass resignation if the PC tries to retaliate against William when Fitzroy is injured in the line of duty, forcing him to back down.
- Belligerent Sexual Tension: Eliza and the Duke's relationship is full of this. While they are friends, they definitely have feelings for each other, and fight often.
- Big Bad Friend: In season 1, the overarching villain, who murdered Henry Scarlet, Eliza's father and the Duke's mentor ends up being Frank, the Duke's best friend and right-hand man.
- Brandishment Bluff: When Eliza and Will are cornered by a masked criminal at the end of season 1, Eliza threatens the man with a gun at close range. The criminal chooses to retreat over trying to close the distance and take out Eliza. The gun, however, ran out of bullets.
- Breaking the Glass Ceiling: One of the main themes with the show is Eliza's struggle to be taken seriously as a woman in the detective business.
- Call-Back: At the end of the first episode, Eliza apprehends her first criminal by poisoning his tea. When she faces him again at the end of series 2 she poisons him via the money he takes from her purse. Will notes that he warned her after the first incident he would have words with her if she used that same tactic again.
- Calling the Old Man Out: At the end of Series 2, Fitzroy gets himself into the station in time to deal with his father, the Chief of Police, when the man is going to have William punished for Fitzroy getting injured on the job. Fitzroy explains that Will has been the best superior he has ever had and he will not stand for the man to be unjustly punished. When his father isn't dissuaded by Fitzroy threatening to resign, Fitzroy reveals that he has already spoken with a majority of the station's detectives and they will all resign in protest over this action. Both the loss of manpower and the inquiry from the news as to why the chief's son is leading this action would destroy his father's political career. The chief backs down from his threats.
- Closet Gay: Rupert Parker. Since someone could not publicly say they were gay in Victorian England, Rupert has to say he isn't ready to be married yet when pressured by his mother. Eventually he enters into a Marriage of Convenience with Tilly Hildegard, who benefits from his wealth.
- Expy: Ms. Scarlet is one for Lizzy Bennet and The Duke for Mr. Darcy.
- Forgiveness: Played with in season 3 "The Heir", when Eliza's client fakes his own kidnapping to extort some money over taking a surprise inheritance which he knew existed for years but avoided because of debts he would have to pay, Eliza is one of the people he defrauded by paying part of her fee with counterfeit bills the police provided her. The other two are either dead or the one who killed the other, so Eliza chooses not to press charges. When seeing the heir at his home, she spots an ornate silver frame with a picture of the heir's wedding on the wall and finds a hidden photo behind. The photo is of the heir's deceased mother and these two things are what were taken from the scene of the man's father's murder years ago. Eliza cannot condone this and regretfully calls the police.
- Downer Ending: Season 3's "The Heir", Eliza goes to great lengths to help a man come into his fortune of 20,000 pounds for him and his pregnant wife. At the end, she discovers he murdered his father and is thus going to the gallows and to inherit nothing. What's worse, his wife will be left with a child and destitute and the victim was an Asshole Victim who had it coming.
- Framing the Guilty Party: By accident. An episode in season 2 has Eliza being arrested for breaking in the the city mortuary and stealing some files, as her mother's ring was found at the scene of the crime. She had snuck into the mortuary (when the ring had slipped off her finger), but it was earlier in the day and she didn't break in—she had earlier duplicated the key to the mortuary—nor had she stolen any files, merely looked at some related to her cases and then put them back.
- Holding the Floor: In the season 1 finale, Eliza does this when the villain has both her and the Duke held at gunpoint, until Moses comes in and takes him out from behind.
- In-Series Nickname: William, also known as the Duke. The nickname stems from his last name, Wellington, being the same as the title of the famous Duke of Wellington.
- Nepotism: Detective Fitzroy only made it to the rank of detective because his father is the Police Commissioner and forced both Scotland Yard and Fitzroy into accepting it, despite Fitzroy's lack of training. That said, Fitzroy is keen to prove himself once the Duke takes him under his wing and proves he has the mettle to be a good detective in his own right.
- Old Cop, Young Cop: The Duke and Fitzroy, respectively. The Duke takes Fitzroy under his wing and teaches him the ropes of being a police detective, and once he discovers Fitzroy is assaulted by another member of the force, personally pays for boxing lessons.
- Parental Substitute: Ivy has been Eliza's mother figure ever since Eliza's mother died when she was small. Once Henry Scarlet dies at the beginning of the first episode, Ivy is the only parent figure she has.
- Put on a Bus: Season 4 ends with William finally telling Eliza he's in love with her, but then getting on a ship to the United States. It was subsequently announced that he would not be returning for season 5, leading to the series being retitled Miss Scarlet to avoid an Artifact Title.
- Spot the Thread: In season 3 "The Heir" Eliza deals with the sudden kidnapping and ransom of an unexpected heir who is set to earn 20,000 pounds. After many twists and turns, including looking into the heir's father's unsolved murder, Eliza realizes the heir killed his father years ago. She notices in the heir's house an ornate silver picture frame with the family crest on it and a photo of the heir's mother hidden in it. These are two things suspected of being taken by the killer.
- The Unfair Sex: Eliza is prone to openly breaking the law and engaging in Cowboy Cop activities that would land her in jail if not for the fact she often is treated as harmless by the police, more a nuisiance than an actual criminal.
- Workaholic: Eliza is accused of being this by the Duke when then discovered that the missing magician they were investigating died by suicide because he was retiring and found life without his job horrendous. As you can imagine, she does not appreciate the comment.
- Yandere: Tilly Hildegard is this with Rupert when she believes Eliza stands in the way of them entering their Marriage of Convenience.
- You Have Failed Me: The season 1 Arc Villain executes two men under him for failing to keep a forger they had kidnapped in their custody and letting Will and Eliza escape.
