A simple case of blackmail gets lethally complicated when “Nameless,” Bill Pronzini’s seasoned private-eye, exposes a nasty scam that involves junior accounts executive Jay Cohalan, his unhappy wife, and a mistress with a serious drug problem. It’s the kind of case “Nameless” likes, because bleeders — the blackmailers, extortionists, small-time grifters, and other opportunists who prey on the weak and gullible — sit near the top of his most-worthless-human-beings list. So he contemplates with pleasure the prospect of putting another one or two of these parasites out of commission, and then returning the $75,000 in cash to its rightful owner. “Nameless” discovers, though, that he is not going to be able so easily to close his Cohalan file — not when he finds his client face down in the middle of a four-poster bed with a bloody, powder-scorched hole behind the right ear. And only by a hair’s breadth does “Nameless” himself escape a similar fate. Aggrieved, cut to the psychological quick by his close brush with death, “Nameless” embarks on a relentless hunt for his unknown assailant in San Francisco’s shadowy underworld. There he encounters bleeders of every ilk — like the loan shark Nick Kinsella, drug dealer Jackie Spoons, punch-drunk boxer Zeke Mayjack, and crankhead Charlie Bright — before he tracks down his quarry. At a deserted backcountry road stop “Nameless,” packing his long-unused .38, attends to the last of a bad business and, in a climax as powerful as it is unexpected, finally confronts his own demons. He maybe even conquers them