The Italian Secretary — Caleb Carr

FOUL WHISPERINGS...
Mycroft Holmes's encoded message to his brother, Sherlock, is unsubtle enough even for Dr. Watson to decipher: a matter concerning the safety of Queen Victoria herself calls them to Edinburgh's Holyrood House to investigate the confounding and gruesome deaths of two young men--horrific incidents that took place with her highness in residence. The victims were crushed in a manner surpassing human power. And while recent attempts on her majesty's life raise a number of possibilities, these intrigues also seem strangely connected to an act of evil that took place centuries earlier...

...UNNATURAL DEEDS
For indeed, the slaying of David Rizzio, music master and friend to Mary Queen of Scots, was an extraordinarily brutal and treacherous act--even for a time when brutality and treachery were the order of the day. Now, the ghosts of Holyrood House are being reawakened by someone with a diabolical agenda of greed, madness, and terror as Holmes and Watson set out to trap a killer who is eager to rewrite history in blood...