The Vanity of Men - Holmes & Watson, #12

It had been over a year since the events that had fractured the highly successful relationship between the London Metropolitan Police and Holmes occurred. And now the newly-promoted Chief Inspector Pomfrett was staring at an unsolvable crime. The sort of crime that Holmes was famous for solving, the sort of crime that being associated with, had resulted in Pomfrett's promotion. There had been an assault on a man in a gay club in Lambeth with little clue as to who or why.
Except that there had been another one with vaguely similar characteristics in Tower Hamlets. And another in Westminster. This was just the sort of case that Holmes could help them with but he refused to budge from his declaration that their association was at an end. When Pomfrett's forceful attempt at reconciliation are met with defiance, his loyal associate Inspector Garrigues offered to try another route.
John Watson. The good doctor Watson was well aware that his boyfriend was no longer involved with the Met, even if no one had been willing to explain what had caused it. When his new friend Jane Grosz (neé Marple) suggested she investigate the rift, Watson is surprisingly willing. When Garrigues approaches him to help on a case that clearly is meant for Holmes, he's convinced that something bigger is afoot.
As Holmes undertakes an investigation where he's forced to disguise himself as a 20-something gym bunny, go under-cover as a personal trainer for an aspiring movie star and use the talents of a Belgian chef (Herc Pirot), a transsexual salon owner (Nancy Drew) and two incorrigible beauty therapists (The Hardly Boys), he also comes face to face with someone who brings with them a warning that Holmes will be punished for his past.
How will Holmes protect himself from his past, at the same time uncovering a crime so heinous in nature that it will shock Chief Inspector Pomfrett to his core? Read on as the 10th book in the Holmes & Watson series takes you back to London to answer this question along with other vital enquires such as, where exactly has Dr Martin disappeared to? What is the only brand of riding crop you should buy? Who could be the mysterious 'puppy master' known for dressing only in leather and tweed? And what sort of person schedules a Christmas Card buying weekend?