The Doctor and his companion Scarlette, head of the the local brothel, solve mysteries and go on adventures. The Faction Paradox are involved, as usual.
Tropes present in The Adventuress of Henrietta Street include:
- Asleep for Days: The Doctor sleeps for a week after losing one of his hearts.
- Bad Black Barf: A symptom of the Doctor's illness. As his condition worsens, his eyes turn black too.
- Fictional Document: The Adventuress of Henrietta Street, in a way, is one, since it's supposedly a piece of nonfiction involving the Doctor. And it also contains a number of other fictional documents, which end up showing that the Doctor writes like he's on something and Sabbath has a stenographer who, stranjly, can't spell.
- Genre Shift: This book was written to emulate a historical document, and reads quite unlike the rest of the series.
- The Man They Couldn't Hang: Juliette is an unusually young example; she's only thirteen. It's implied she'd attempted to hang herself, but not only did she not do it properly, the Doctor showed up to rescue her.
- Marshmallow Hell: Lightly implied; Katya, whose buxomness is one of her defining characteristics, bids farewell to Fitz in such an affectionate manner he nearly suffocates.
- Old, New, Borrowed and Blue: The Doctor has to get married because it'll somehow save the world from extradimensional baboons. Fitz mentions it's too bad they can't bring the TARDIS into the chapel, because it would count as all four.
- Psychic Surgery: Some vague version of this happens to the Doctor, although the details/explanation are concealed by the semi-Lemony Narrator who basically admits he/she doesn't know exactly what happened.
- Sick Episode: The Doctor starts feeling a bit poorly at the beginning of the book, and things get really dramatic and life-threatening by the climax.
- Switching P.O.V.: The Adventuress of Henrietta Street largely averts this, being mostly narrated by an unnamed historian, but uses Scrapbook Story to get some of the same effect.
- This Bed of Rose's: The Doctor, Fitz, and Anji are staying at Scarlette's brothel for most of the novel, and the young ladies working there help them to save the world from extradimensional apes and whatnot.
- What Do You Mean It Wasn't Made On Drugs: The entire plot revolves around stopping interdimensional apes. There's a hunt involved. It's weird.
- Wild Samoan: Tula Lui is a teenage girl who's the last survivor from some Polynesian island, virtually never speaks, goes around killing people, and is the closest thing that 18th-century gentleman villain Sabbath has to a real friend. When he used to have a social life he'd bring her to parties because he apparently thought it was funny when she snarled at people.