Murder on Cold Street by Sherry Thomas

Inspector Treadles, Charlotte Holmes’s friend and collaborator, has been found locked in a room with two dead men, both of whom worked with his wife at the great manufacturing enterprise she has recently inherited.

Rumors fly. Had Inspector Treadles killed the men because they had opposed his wife’s initiatives at every turn? Had he killed in a fit of jealous rage, because he suspected Mrs. Treadles of harboring deeper feelings for one of the men? To make matters worse, he refuses to speak on his own behalf, despite the overwhelming evidence against him.

Charlotte finds herself in a case strewn with lies and secrets. But which lies are to cover up small sins, and which secrets would flay open a past better left forgotten? Not to mention, how can she concentrate on these murders, when Lord Ingram, her oldest friend and sometime lover, at last dangles before her the one thing she has always wanted?