Showing Sharper Than a Serpent's Tooth by Simon R. Green

The Nightside – the secret heart of London – is a dark, shady place, full of dark, shady characters. A corrupt place, where both dreams and nightmares come true, where anything can be bought for the right price, and where it is forever 3 a.m.

But to private detective John Taylor it is home, and he won't allow his home to be destroyed - especially by his own mother.

Taylor knows he is the only one who can stop her from obliterating the Nightside, a place she created. The problem is, he also knows that whatever action he takes, the Nightside – and the rest of the world – will be doomed.