The fourth Simeon Grist p.i. mystery (Skin Deep, etc.), which would be little more than routine were it not for the esoteric fire references bandied about by the torcher of Skid Row derelicts who's known to the police as ``the Crisper'' (though he himself prefers the name ``Incinerator''). Simeon enters into the serial murders when one of the victims turns out to be a lost, disoriented millionaire suffering from Alzheimer's, and when his daughter announces to the press that she's hired Grist to find out who killed him. The trail leads to the library and to a tall thin, blond man with a clubfoot who drives a Mazda and wears a black rubber raincoat. And, as it happens, was in love with Grist's sometime lover Eleanor Chan at college, which explains why the Incinerator keeps taunting Simeon with clue-filled notes. Eventually the two meet up at L.A.'s Renaissance Pleasure Faire, where the Haunted House and the Toy Railroad hold more than their share of corpses--and matches. Shallow psychoanalyzing and sketchy plotting, but those fire references will tweak the synapses. Otherwise: just one more serial killer.