THE GOD OF THE HIVE, by Laurie R. King

10/series. Once again, Laurie R. King puts Mary Russell and her husband Sherlock Holmes through the wringer, this time bringing in the next two Holmes generations: Damien Adler, son of Sherlock and Stella Adler, and Damien's delightful three year-old daughter. Everyone's on the lam: Holmes makes his laborious way off the Orkney Islands where the action starts. Mary, with the granddaughter, flee the islands in a new-fangled aeroplane, but with catastrophic results. Enter enigmatic hermit Robert Goodman, a shell-shocked young man living deep in a forest in the Lakes District. The Holmes' separation makes for a fascinating story, you're almost getting two tales for the price of one.
They return to London, not knowing if the other is alive, and find that a new "god of the hive" has arranged Mycroft Holmes' disappearance. Skulking from bolt-hole to bolt-hole, Mary lock-picks her way into her brother-in-law's apartments, as well as a couple of places she should have known better than to attempt. Sherlock, master of disguises, keeps missing his wife, literally and figuratively. The denouement is satisfyingly chilling. This series could of course be read as stand-alones, but why deny yourself the pleasure of reading the entire dozen books. Start with The Beekeeper's Apprentice and you'll be hooked. It's a 4.5.