At the end of the previous novel - The Dead Can Wait - we left Dr/Major Watson badly burned and in a German Field hospital after cracking the case and confronting the antagonist in No Man's Land.
Since then, he has been transferred to a German POW camp where he has been tending the other prisoners and biding his time.
A prisoner exchange is being arranged, and as he is of the age and profession deemed appropriate to hand back, Watson prepares to leave. But an old case casts a long shadow, and the German Agent/Spy, Von Bork - from the last Holmes story, 'His Last Bow' - is on the prisoner exchange committee and gets Watson pulled out at the last minute in revenge for the Spy's humiliation at Holmes and Watson's hands.
Von Bork's revenge continues, as he gets Watson and his batman from the camp transferred to one of the worst camps further within Germany. On the way there, Watson is greeted by Von Bork who takes the opportunity to rub salt in the wound and then has Watson's batman shot in cold blood.
Watson arrives at the new camp, bleak, cold, where prisoners are charged twice the going rate for supplies and food outside of their budget is mostly sawdust and rat meat. Watson is greeted with suspicion and distrust, has his belonging stolen and then is thrown into solitary confinement for possession of an escape plan map he knew nothing about.
Released from the prison within the prison, the Camp Commandant, who learnt his trade of salesmanship in America before the war, tells Watson that he had been sent with a dossier of Watson's being a spy, an agent provocateur and generally someone who was not supporting the British effort in the conflict - a troublemaker and rabble rouser. The Camp Commandant, Mad Bill, now makes it known that is not true and sends Watson on his way back to his fellow prisoners.
His fellow inmates apologise to him, and Watson discovers an escape plan which makes him feel distinctly uneasy - and begins his investigation.
Meanwhile, back in London, Georgina Gregson is working for a POW Welfare Parcels Association, trying to find out where Watson is. Her tenacity knows no bounds and she sweet talks a senior Army officer into helping her - and ends up involving the deadly Miss Pillbody, aka Ilse Brandt, a Sie Wolfe/Sea Wolf - German Naval Intelligence Agent and trained killer.
The third strand is, of course, the Great Detective. While Watson investigates and does his best to survive a punishing German winter in his POW Camp, and Mrs Gregson seeks a way to free him, Holmes has been approached by Von Bork who offers a bargain, albeit a devilish one.
Von Bork will ensure Watson's freedom and return to Britain under one exchange deal - Holmes must take his place.....
A many convoluted turn of plot and location, this third novel in the Dr Watson thriller series had me race through it again.
Another library book so being returned this weekend, hoping I can find the 4th (and currently last in the series) novel....