This is at least the third book I've read about a mystery set in London with magical/supernatural elements thrown into the mix, but it still brought something new to the much loved genre. The main character, Peter Grant, is a newly minted PC guarding a murder scene during an routine night shift when he sees his first ghost. Like any good copper, he attempts to take the ghost's witness statement. Later he is tapped by Chief Inspector Nightingale, the last wizard of Scotland Yard, for a very unusual training placement as magician's apprentice. This murder is just the beginning. Random rage-fueled attacks begin to take place all over the city. Worse yet, the very rivers are gearing up for war if Grant can't find them a diplomatic solution.