It's 1865, and Charles Lenox is a gentleman, the younger brother of baronet Sir Edmund Lenox, living in London and pursuing his hobbies and passions.
One of his hobbies is planning foreign travel. He rarely takes these carefully planned trips, because one of his passions is solving crimes. He has a friend who sometimes assists him, Dr. Thomas McConnell, but that fact and his ability to deduce interesting facts about people from evidence that others miss is really where the resemblance to that other great Victorian-era detective ends. Lenox is not a professional, a consulting detective. He's an amateur, doing this for love and usefulness. When his neighbor and friend, Lady Jane Grey, asks for his help, he immediately cancels his latest planned trip.
A former housemaid of Lady Jane's, Prudence Smith, has died, either by murder or suicide, at the home of her new employer, George Barnard. Barnard is an acquaintance, and also the head of the Royal Mint, and is more interested in preventing scandal than finding the truth.
It's a delicate case, and gets a bit more challenging when Inspector Exeter, a senior man at Scotland Yard but inclined to be resentful of Lenox's interference, is assigned to investigate it.
Finch leads us through an intricate puzzle involving Barnard's two nephews, both living with him, Prudence Smith's multiple lovers, as well as two Members of Parliament and a wealthy industrialist of low birth who are all guests in the Barnard home. Everyone with even a remote motive has an alibi, and everyone without an alibi seems to have no conceivable motive.
And then one of the Members of Parliament is murdered, during Barnard's annual ball. It seems improbable that the two murders are unrelated, yet what connects them? There's also the awkward fact that the dead man had been one of the best suspects in the murder of the maid, and the nephew that had no alibi for her murder, has an unbreakable alibi for the murder of the MP: Lenox's brother Sir Edmund was watching him the whole time.
This is a carefully built puzzle grounded in the personalities and constraints of the different players, with economical but effective character development of each significant individual. I did find the epilogue a bit drawn out, and there mainly, I think, to lay the groundwork for developments in later volumes in the series, but that's a minor complaint in a generally very satisfying mystery.
If you enjoy a good mystery, this is one to seek out, especially since, if you enjoy this one, there are several more already in print.
I received a free electronic galley of this book from the publisher via NetGalley.