A year after the events of The Gentleman's Guide to Vice and Virtue, Felicity Montague is living in Edinburgh and working in a bakery. To escape the attentions of her boss, who would like to marry her, and finally get somewhere with her dream of becoming a doctor, she comes back to London.
There, she hears about the opportunity she's dreamed of: A doctor she idolizes is marrying her estranged childhood friend Johanna. Together with a mysterious woman named Sim she travels to Germany, and is soon embroiled in another adventurous quest through Europe...
- Asexuality: Felicity is asexual, and aromantic too. (Although, as the book is set long before those terms were invented, they were never used in-universe.)
- Aw, Look! They Really Do Love Each Other: Felicity and Monty get a few moments like this. Like when Monty accompanies Felicity to the university, or when he and Percy follow her across Europe because they were so worried. Felicity even lets them hug her when they save her from Doctor Platt!
- Badass Bookworm: Felicity, as in the last book. Johanna, too, even if she's not really into fighting.
- Big Brother Instinct: Monty and Percy towards Felicity, as in the last book. They clearly worry about Felicity when she starts talking about going to Germany out of nowhere.
- Big Little Brother: Well in this case, sister. It's stated that Felicity grew significantly since the events of the first book, making her taller than Monty.
- Big Damn Heroes: When Felicity and Johanna are captured and supposed to be shipped back to London, it turns out that the captain of the ship is Scipio, the honorable pirate from The Gentleman's Guide to Vice and Virtue, and Monty and Percy are on board, having followed Felicity because they were worried.
- Broken Pedestal: Felicity idolized Doctor Platt, and therefore the fact that he was just using Johanna and never had any intention of teaching her medicine hurts her quite a bit.
- Hates Being Touched: Downplayed with Felicity. It's not a really big thing, but when she lets Percy and Monty hug her after they save her from being a hostage it's a clear sign how happy she is to see them.
- Innocent Bigot: Felicity. She has problems with Monty and Percy's relationship because she was raised to think gay people are depraved, though she keeps those thoughts to herself and does get over that. It's also what caused her friendship with Johanna to end, as Felicity couldn't really understand that just because Johanna likes girly things that doesn't mean she's stupid. Also towards Sim, who is a brown woman wearing a hijab. She does learn to let go of her prejudices though.
- MacGuffin: Johanna's mother's notes.
- Magical Realism: More so than the last book, what with dragons being real in the end.
- Missing Mom: Sim's mother is never mentioned. Felicity's mother seems to still be alive, but she doesn't have any contact with her. Johanna's mother apparently left the family when Johanna was young, and turns out to have been a scientist who died on one of her expeditions.
- Nice Guy: There isn't really anything wrong with the baker who wants to marry Felicity in Edinburgh, she's just asexual and aromantic and therefore not interested in him or anyone for that matter. Also, she doesn't want to live her life as a bakers wife, she wants to become a doctor, which wouldn't be possible if she marries the man.
- Nice Job Breaking It, Hero: Felicity tries to find Johanna after she disappears from her wedding. This however leads Doctor Platt in her direction, and as it turns out, Doctor Platt is evil and only using Johanna for his gain, and her disappearance was deliberate.
- Out of Focus: This book is Felicitys story, told from her perspective. Therefore Monty and Percy, who live happily in London, are much less part of the story then before.
- Road Trip Plot: Much like the last book, the main characters spend most of the time travelling.
- Pirate Girl: Sim. She actually turns out to be a pirate princess, too, as her father is the "king" of the pirates.
- We Used to Be Friends: Felicity and Johanna used to be very close as children. They had a falling out sometime before The Gentleman's Guide to Vice and Virtue and haven't talked to each other ever since. While Felicity remembers Johanna becoming mean to her because she wasn't girly enough, it is later revealed that Felicity was the one whose behavior changed first, as she didn't really realize that just because Johanna likes girly things it doesn't mean she can't also like science. They make up over the course of the book, though.
- You Are Worth Hell: After having cut their ties with their rich parents in the last book, both Monty and Felicity have to work and have had to get used to a different style of living. They're not really all that sad about it, given that at least now they can be true to themselves.