The Black Country

This is apparently the 2nd in a series by Alex Grecian written about the "murder squad" of Scotland Yard that was inaugurated in the late 19th century (i.e., Victorian era), after the Jack the Ripper cases failed to be solved. I could not find much about this unit, but in an author Q & A, Grecian claims it was and is a real unit and that his characters are based loosely on actual men in the unit. Given the unit's purview (i.e., the London metropolitan area), it's a little surprising that, in this story, they have been sent to a small village in coal mining country, Blackhampton, to find a missing family--or at least the parents and the youngest child. Inspector Walter Day and his sergeant, Nevil Hammersmith, have come on ahead of the Yard's first forensic pathologist (also based on an actual person), Dr. Bernard Kingsley. The villagers are a closed lot, highly superstitious, and seem to want to thwart efforts to find the missing family by any means, including drugging the two Yard policemen.  To complicate the picture, there is a terribly disfigured American who has come to the village on a quest for vengeance. The village itself is sinking (sometimes slowly and sometime rather abruptly) into the myriad tunnels dug underground in search of coal; it and the unseasonably cold weather both are characters in this mystery as well. It takes a while to sort out who did what. Two of the older children from the missing family are being looked after by a housekeeper and the local school teacher, and it is clear that they know something about their missing younger brother. A couple of "Interludes" set during the Civil War in the U.S. provide the motivation behind the American's quest and fill in some history on one of the people in the village who is particularly keen to find the missing child. Tied into the story is the fact, initially hidden from the police, that over half the villagers have come down with an illness which is killing them off at an alarming rate. Hammersmith may soon be among them. Day's very pregnant wife makes an appearance in the village, on her way to stay with her sister, and adds dimension to the character of Inspector Day.
Altogether this is a very atmospheric setting, with well developed characters and an engrossing plot line. Not too improbable and yet tricky to figure out. If you like historically based mysteries, this would certainly satisfy.