The Infidel Stain by M. J. Carter

It is 1841.  Jeremiah Blake and William Avery, who met and worked together in India, have both returned to England but haven't seen each other in three years.  Avery, now a gentleman with a wife and baby on the way, goes to London when he receives a message from Blake asking him to come.  He finds Blake, much the worst for wear, living in the slums of London and scratching out a small living by being a private investigator.

Blake's newest case has him needing help and he turns to Avery.  A Lord has approached him about investigating a series of murders.  Several men who run printing presses have been killed in grisly fashion.  The newly formed police force doesn't seem that interested in solving the case.  As Blake and Avery investigate, they determine that the printers were not only of the normal sort, but all had a sideline in pornography.  Even more telling, all seem to have known each other twenty years ago in the revolutionary movement now known as the Chartists, who are determined to win the vote for all men.

The bodies continue to mount up.  Informers are bountiful and it is difficult to make any headway.  The pair befriend a young girl who sells on the street and her brother, who has been falsely accused and headed for transportation to Australia.  Can they save this small family along with solving the murders?

This is the second case in the Blake and Avery series.  As with the first, the interest lies not only in the narrative but in the meticulously researched history that brings a Victorian environment alive.  The interplay between Blake and Avery is also interesting, each needing the other but very different in their understanding of the world and how they fit into it.  This book is recommended for mystery readers as well as historical fiction ones.