Spoilerific review behind the cut.
Teal deer (that's what my husband is now calling 'tl;dr'): This story is very skippable.
The Doctor and Rose in the Regency, meeting the mysterious Chevalier d'Eon. What's not to love, right?
I'd seen the ranking of this story on the Time Scales, which rated it lower than "Infamy of the Zaross", but I thought, since they rated IotZ high and I thought it was pretty meh, maybe I just have different tastes than others and I will like "Sword of the Chevalier" better. I was wrong.
First, you've got the Chevalier. In case you're not familiar with the Chevalier (I only know about the real Chevalier because of a mention in one of Neil Gaiman's works), he was a French spy who people suspect was actually a woman. The Doctor gives his/her brief history: brought up as a man, worked in England as a spy for France, was exiled to England after he/she lost favor at the French court and lived there as a woman, claimed to be a man to return to France and was pardoned only on the condition that he/she live as a man there. So much potential there for this character to lead the Doctor and Rose into a web of intrigue and mystery.
Then there's the antagonist(s), a member of the Consortium of the Obsidian Asp that is three individuals in one body with three faces and voices. I do not remember if they named their race during the audio; they mostly identified themselves with the Consortium, which the Doctor described as a loose organization of thieves and other chaos makers. This particular member has one dead individual; the remaining two were named Joxer and Hempel, one male and one female, so I will refer to them as Joxer. Joxer is a slave trader and is on Earth to capture humans and sell them. They considered their race (whatever it was) to be superior to humans, and so they were entitled to enslave them. The dynamic between the two personalities reminded me of Mr. Croup and Mr. Vandemar from Neverwhere, though neither were simple like Mr. Vandemar.
Put these together and you should have a thrilling story. You have the spy and master swords(wo)man on one hand. On the other hand, you have a dual individual to explore, and if that doesn't pan out, that's two intelligences the Doctor has to defeat. But no, the writer didn't opt for any of that. At this point in his/her life, the Chevalier is exiled to England and rather downtrodden (since the English nobles don't like him/her either), resorting to putting on swordsmanship shows to make money. His/her role in the story is to be supercilious and insult the Doctor's abilities.
Joxer, meanwhile, is just a villain. They prey on the attendees of a masquerade party (a great deal, since this three-faced being can hide behind a mask) thrown by a noble they've bribed, secreting them away, and then decide that since humans would sell for more if the supply dried up, they should capture about fifty and destroy the planet by releasing poison bombs into the atmosphere. The individuals never argue with each other, or come up with new ideas to solve problems. In my opinion, the only reason the character was designed this way was so that it could say what it was thinking out loud.
This resulted in the following plot: The Doctor and Rose meet the Chevalier at a swordfighting demonstration. The Doctor detects the Consortium on Earth and goes to stop whatever they're doing, and the Chevalier tags along. They end up at the party. Rose is captured and spends some time trying to unlock the prison cells with the sonic, which she happens to have. Meanwhile, the Doctor and the Chevalier meet up with Joxer and there's grandstanding on both sides, then Joxer leaves to go arm the poison device after setting their zombies (this isn't random - this is explained but unimportant) on them. The Chevalier grabs two swords off the wall and they kill the zombies.
The heroes regroup and find Joxer about to turn on the device that will fire the poison bombs. Joxer mocks them some more, saying how inferior they all are and how they never cede to inferior species; they only defer to superior species. The Chevalier challenges them to prove their superiority through a swordfight, and beats them while the Doctor attempts to disable the device. Then he smashes the device with his sword. Joxer mocks him, that the inferior lifeform resorted to base violence. The Doctor tells them to scan him. They surrender to him, and he tells them to release the humans and buy back and release all of the other slaves they've ever sold.
In summary, the bad guys did some bad things, and the heroes won through a combination of swordfighting and having been born Gallifreyan.
There was really nothing redeeming about this plot. There were no unwinnable situations saved by clever thinking. There were no puzzles for the audience to figure out; the moment Joxer said that they would only defer to a superior race, you knew how the Doctor was going to win. There were snatches of clever dialogue but not much. The writer opted instead for lots of the Doctor being foolish and the other characters mocking the Doctor, rather than good banter.
Which brings me to the subject of Rose. I never thought I would ever say this, but Rose was really shortchanged in this story. She did absolutely nothing. It reminded me of "Terminus", which was Nyssa's last story and it was all about her, so the writers needed to get Tegan and Turlough out of the way - they get trapped in a ventilation duct for two whole episodes. Rose spends the first part of the story mocking the Doctor (which is out of character; she used to tease him, yes, but not to this extent), and then is dumped in prison for most of the episode. Once she figures out how to use the sonic, she does help the others get out of the cells, but that's her entire contribution to the episode. This story would have been better with no companion, so that either the Chevalier or Joxer got more development time. Well, maybe in the hands of a different writer, it would.
I think the writer was trying to parallel the Chevalier and Joxer - the individual who is both man and woman and the two entities who are one individual - but any message got lost in amidst Joxer repeating his opinions about superiority and inferiority, and certainly the Chevalier didn't learn anything from this adventure.
Performance-wise, DT was great, though again I'll say he was better in the first series. He's an amazing voice actor, and I imagine that he was jumping around that studio during the swordfighting scenes. BP still didn't sound a thing like Rose, though admittedly she wasn't given any real Rose material to work with. The Chevalier did a good job sounding androgynous, and the two voice actors for Joxer were great - they all would have shone if they'd been given meaty parts.
So, one more story in this series to go, and then back to praying for more series, preferably with Martha or Donna and especially with James Goss doing ALL THE WRITING!