Too Old a Cat — Warren Murphy

It's trouble in paradise when a mafioso hires Trace to tail his wayward wife, who's run off and joined a crazed sex cult. As the case involving the gangster's gal turns deadly and two cantankerous cops are chomping at the bit, Chico threatens to leave for good. With all the loose ends splitting apart, Trace must track the deadly string across New York City before the bodies start piling up.