This fourth Victorian occult mystery finds brilliant but erratic detective Sir Maurice Newbury and his intrepid sidekick, Veronica Hobbes, seeking a legendary assassin who removes her victims' still-beating hearts. Known as the Executioner, this beautiful, ageless woman is covered in elaborate symbols and has a clockwork heart, which keeps her alive but unable to feel. Several factors complicate the case: Prince Edward has hired Newbury to unearth enemies to the crown, as the queen, her decaying body preserved in a monstrous machine, has grown dangerously paranoid. Meanwhile, Victoria worries that the arcane rituals Newbury performs to protect her sister from her seizure-inducing prophetic visions are killing him. As Newbury investigates the Executioner, he learns that she is targeting the queen's agents himself included but the real mystery is who hired her. Mann's blend of steampunk, sorcery, and a Sherlock Holmes-style detective story is winning, packed with period details and clever, if convoluted, plotting. A strong focus on black magic and many vivid, gory scenes will also appeal to horror fans.--Hutley, Krista Copyright 2010 Booklist