Mrs Hudson must step into action once more.

It's summer in London, and things are quiet. But while Sherlock Holmes and Dr. Watson chafe at their inactivity, a train carrying a vital secret is entering a tunnel in an obscure region of the Balkans - never to be seen again.

The train is only the beginning. The missing message must be found and decoded, and a diplomat's wife must be rescued from the clutches of a pernicious blackmailer.

The nation is in danger, and if a diplomatic scandal of disastrous proportions is to be avoided, Sherlock Holmes' brilliance may not be enough... Mrs Hudson and Flottie her assistant will once again turn detective.

From the Richard & Judy-featured author of The Conjuror's Bird, back by popular demand, the first new Holmes & Hudson novel for several years.