I was my dad's vinyl-wallah: I changed his records while he lounged around drinking tea. And it's why, when Dr Walid called me to the morgue to listen to a corpse, I recognised the tune. Something violently supernatural had happened to the victim, strong enough to leave its imprint. Cyrus Wilkinson, part-time jazz saxophonist, had apparently dropped dead of a heart attack just after finishing a gig in a Soho jazz club. He wasn't the first. There were monsters stalking Soho, feeding off that special gift that separates the great musician from someone who can raise a decent tune. That's the thing about policing: most of the time you're doing it to maintain public order. And maybe once in a career, you're doing it for revenge.