"The Lantern's Dance" by Laurie R. King

Another winner from Laurie R. King!  The Lantern's Dance is the eighteenth Mary Russell/Sherlock Holmes book, and a thoroughly enjoyable entry into the series.
This review contains SPOILERS for the series, not just for this book, so beware!  Jump to the movie-style rating if you want to avoid spoilage.

Mary Russell and Sherlock Holmes already on their way to France when Holmes's son, Damian Adler, alerts them to the fact his home has been broken into.  Fearing that some of their enemies may try to...