While Nan and Sarah's adventures are firmly set amidst the rest of Lackey's Elemental Masters series, with A Study in Sable she also deftly blends her own lore with that of Sherlock Holmes and asserts that Holmes' partner, John Watson, is an Elemental Water Master who helps Sherlock with the more arcane cases that don't interest the detective, while also playing down his own part when he writes the stories that most people hear about. In A Study in Sable, Nan and Sarah move to London and are asked to help John and Mary Watson, and by extension Sherlock, in various cases.
The Bartered Brides takes place early in the period of Sherlock Holmes stories known as the Great Hiatus, that is, the time between Sherlock's supposed death at the end of "The Final Problem" and his reappearance in "The Adventure of the Empty House." When Sherlock, in disguise, comes to Nan, Sarah, John and Mary and explains that he is going to use his newly found deceased status to secretly hunt down the rest of Professor Moriarty's organization, the four are left in London to help Inspector Lestrade with a new mystery, and one they really wish they could have Sherlock's eyes and deductive reasoning on. Instead, they will have to use their own unique skills in order to determine exactly what is going on.
Lestrade contacts John when the headless bodies of young girls start washing up on the Thames River. The group quickly realizes a few things; one is that besides the fact that they are young, impoverished girls, the only thing they really have in common is that they are all dressed as if they are getting married, the other is that this case could easily be the work of someone more in their line of work rather than a simple serial killer. These bodies could be created by a necromancer. Unfortunately, given the rarity of such a magic user, no one, not even Lord Alderscroft, can figure out exactly what the killer is up to.
Lackey weaves an interesting tale in The Bartered Brides and, as usual, the chapters flip-flop between following the protagonists and their enemy. So, while the heroes don't know what is going on, the reader gets a great deal of insight into the necromancer's plans. The result is an amusing cat-and-mouse chase where the two sides end up frequently changing which is the cat and which is the mouse as they all learn more information about their particular adversaries.
The Bartered Brides is a fine addition to the series and adds more lore to both the Elemental Masters series and to Lackey's version of the Sherlock Holmes franchise.