The Wolves Of London (Obsidian Heart, Bk. 1)

Psychology professor Alex Locke is an ex-convict, forced back into the criminal underworld when his daughter is threatened. After he agrees to steal a mysterious Obsidian Heart, Locke is pursued by unearthly assassins known as the "Wolves of London." Soon he discovers the heart can enable him to travel through time, and while it bestows him with his own dark powers, it also corrupts . . .