The Deep Blue Good-Bye — John D. MacDonald

One look at Cathy Kerr and you could tell there was nothing life hadn't done to her. She was innocence turned helpless desperation, great brown eyes gone mournful and hopeless, tender illusion changed to memories of unutterable shame -- all because of the smiling freckle-faced stranger named Junior Allen. Cathy had nowhere to turn -- except to another smiling stranger -- that big, loose-jointed boat burn, that slayer of small, savage fish, that beach walker, gin drinker, quip-maker. That man named Travis McGee -- who was a walking pillar of cold rage as he followed the depraved wreckage of Junior Allen's trail...