Wild to Possess by Gil Brewer (Monarch Books #107, 1959)

Gil Brewer started off with hits for Gold Medal, but all was not milk and honey for the noir author, as Bill Pronzini notes at The Mystery FIle:

His success had begun to wane.  Overexposure, a slowly changing market, the darkening nature of his fiction. . . these and intangibles had led to a steady decline in sales of his Gold Medal and Crest originals after the high-water mark of 13 French Street, to the point where Fawcett decided to drop him from its list.  In his world-by-the-tail decade, he published twenty-three mostly first-rate novels under his own name, fifteen of those with Fawcett; between 1961 and 1967, he published a total of seven mostly mediocre novels – one last failure with Gold Medal (The Hungry One, 1966) and the other six with second-line paperback houses (Monarch, Berkley, Lancer, Banner).

Wild To Possess is one of those titles from Monarch. The protagonist, Lew Brookbank, has been bouncing around Florida for six months, running away from the craziness of his life — his wife, Janice, had been having an affair with a boat bum they knew, Deke Clarkson, and when he went to the guy’s boat to catch and confront them, he found both their dead bodies, shot up.

Freaked out, he took the boat out, dumped their bodies in the ocean, and let the boat drift off.  He had a Luger and figured the cops might try to pin the murders on him. He then started to wander, planted himself in Gulfville, a small Florida town, got a girlfriend, Rita, and tried to forget…only, he drinks more and more trying…

And one day, while posting real estate signs along the road, deep in the flora and fauna, by the swamps,  he overhears a man and a woman talking about a kidnap for ransom plot.  He follows them to the woman’s house and, like an Orrie Hitt peeper, he watches them from the window and listens to their scheme: they are going to kidnap his wife, whose mother is rich, and demand $250,000 in ransom. They are Isobel and Ralph; his wife is Florence. But they don’t plan to release Flo, they can’t; they are going to murder her and run off with the loot…always the loot, the payday, easy money, ill-gained cash, the greenbacks that drive many a noir and Brewer character…