Why Mermaids Sing

It's September 1811, and someone is killing the wealthy young sons of London's most prominent families. Partially butchered, with strange objects stuffed in their mouths, the bodies are found dumped in public places at dawn. When the grisly remains of Lord Stanton's eldest are discovered in the Old Palace Yard beside the House of Lords, the local magistrate turns to Sebastian St. Cyr, Viscount Devlin, for help.

Ranging from the gritty world of London's docks to the luxurious drawing rooms of Mayfair, Sebastian confronts his most puzzling -- and disturbing -- case yet. With the help of his trusted allies -- his young servant Tom, the Irish surgeon Paul Gibson, and his lover, Kat Boleyn -- Sebastian struggles to decipher a cryptic set of clues that links the scion of a banking family to the son of a humble vicar. For as one death follows another, Sebastian comes to believe that the murderer has both a method and a purpose to his ritualized killings, and that the key to it all may lie in the enigmatic stanzas of a haunting poem...and in a secret so dangerous that men are willing to sacrifice their own children to keep the truth from becoming known.

This is #3 in A Sebastian St Cyr Mystery.