Note: According to the publisher, this is a "very long novella", but at 47,000 words, it's considered a novel by ISFDB. Although the genre of the novel is steampunk, it's not clear how much SF content is present. It's also not clear how much of the work was contributed by Kage Baker, who had died in 2010, 2 years before the novel appeared.

Synopsis: Nell Gwynne's is far more than simply the finest and most exclusive brothel in Whitehall; it is in fact the sister organization to the Gentlemen's Speculative Society, that 19th-century predecessor to a certain Company… Lady Spies on vacation from their undercover lives as High-Class Call-girls.