The Hollow of Fear: The Lady Sherlock Series, book 3 (Lady Sherlock Series, 3)

Charlotte Holmes, Lady Sherlock, returns in the Victorian-set mystery series from the USA Today bestselling author of A Conspiracy in Belgravia and A Study in Scarlet Women, an NPR Best Book of 2016.
Under the cover of "Sherlock Holmes, consulting detective," Charlotte Holmes puts her extraordinary powers of deduction to good use. Aided by the capable Mrs. Watson, Charlotte draws those in need to her and makes it her business to know what other people don't.
Moriarty's shadow looms large. First, Charlotte's half brother disappears. Then, Lady Ingram, the estranged wife of Charlotte's close friend Lord Ingram, turns up dead on his estate. And all signs point to Lord Ingram as the murderer.
With Scotland Yard closing in, Charlotte goes under disguise to seek out the truth. But uncovering the truth could mean getting too close to Lord Ingram--and a number of malevolent forces.