Mary Russell is used to dark secrets – her own, and those of her famous partner and husband, Sherlock Holmes. But what about the secrets of the third member of the Holmes household: Mrs. Hudson? Russell’s faith and affection are suddenly shattered when a man arrives on the doorstep claiming to be Mrs. Hudson’s son.

What Samuel Hudson tells Russell cannot possibly be true, yet she believes him – as surely as she believes the threat of the gun in his hand. And when the scene is discovered – a pool of blood on the floor, the smell of gunpowder in the air – the most shocking revelation of all is that the grim clues point directly to Clara Hudson.

To uncover the truth, a frantic Sherlock Holmes must put aside his anguish and push deep into his housekeeper’s secrets – to a time before her disguise was assumed, before her crimes were buried away.

There is death here, and murder, and trust betrayed. And nothing will ever be the same.