By R.N. Morris, a sequel to a previous book which I think I should now read.
This murder mystery takes place in tsarist St. Petersburg in the 1860s. There have been recent reforms but the country is still very much locked into class divisions and corruption. Our detective is Porfiry Petrovich, who was a character in Dostoyevski's Crime and Punishment (which I think awaits me on my list of 100 Must-Read Novels). In some ways he reminded me of D.S. Dalziel from Reginald Hill's Dalziel and Pascoe series, though not quite as rude to his underlings.
It opens with the poisoning of a doctor's wife and son and of course other murders crop up which turn out to all be connected. A good read in my opinion.