I have to admit that while I enjoy this series very much, the last book, When Falcons Fall, was not one of my favorites. I was happy that Where the Dead Lie is very much back to form. All of the characters I like are here: Sebastian, Hero (and Simon), Jarvis, Tom, Kat, and others. 
 Sebastian has a new mystery when the body of a teenage boy is found. The boy has been horribly tortured before his death, but there aren't many clues to follow, mostly because the boy is one of London's poorest. Hero is inspired to write a new series about the poverty among London's children, especially those who had parents transported and are left to survive on their own as best they can. Both Sebastian and Hero are dealing with personal issues involving his niece and her mother. 
 Ms. Harris does her research and it shows here. I could envision the smoke and despair in Clerkenwell, the opulence of society and the brothel at Number Three Pickering Place, and the dank ruin of the shot factory from the descriptions in her writing. 
 A bit of editorializing here: some reviewers were upset because Sebastian and Hero didn't do more to help the poor of London. This was one of the times in England's history when the gap between rich and poor was tremendous due to enclosures, the men lost to the Napoleonic wars, and the beginnings of industrialization where the poor worked long days for a pittance. The wealthy mostly did not care about the poor, one of the reasons that the laws Parliament passed were so hard on the weaker citizens who often turned to crime to survive. Shining a light as Hero does and avenging their deaths as Sebastian does was much more than most of the rich did in those times where poverty was so widespread. /done with editorial/ 
 As this is a continuing series, I didn't mind that the mystery wasn't completely solved and will be continued in the next book. C.S. Harris is an author that I pre-order as soon as I can and wait anxiously for the next book. My one quibble is that I hoped to learn more about Sebastian's father, but hopefully that will be addressed further on in the series.