Charlotte Holmes—aka Sherlock Holmes—becomes entangled in a puzzling missing person case that hits close to home for her beloved Mrs. Watson in this Victorian-set mystery from the USA Today bestselling author of A Ruse of Shadows.

It’s been three years since Charlotte Holmes struck a decisive blow against Moriarty's operations in Britain, three years of relative calm and benign developments. In a buoyant mood, everyone gathers at Lord Ingram's seaside cottage in North Devon for what promises to be a perfect summer holiday. Until Mrs. Watson receives an invitation from Mrs. Carstairs, her long-estranged sister, to attend a house party nearby.

Mrs. Carstairs has married spectacularly well. She is the mistress of a great manor, a doyen of all domestic arts, and still an unforgettable beauty. Now she clamors for a reconciliation with her sister. Mrs. Watson does not trust Mrs. Carstairs's motives. Yet she cannot help but feel tremors of the old admiration for this once-beloved sister. 

Then Mrs. Carstairs disappears without a trace. The next day a woman is discovered floating on the waves, her build and coloring matching those of Mrs. Carstairs. But her husband insists that the corpse fished out of the Bristol Channel cannot be his wife. So where is the real Mrs. Carstairs? Would she have purposely dragged Mrs. Watson into a murder investigation? Or was it Sherlock Holmes's involvement that she needed from the very beginning?