The Deep Blue Goodbye by John D MacDonald (1964) Fawcett Publications

The first of the Travis McGee novels – where the hero is manipulated into looking into a woman’s stolen inheritance of ill-gotten gains.  Her father died in prison, convicted of killing another soldier, and never told his wife and daughters where he hid his treasure.  But he hinted enough to his cell mate to have the man move-in with his daughters when he got out of prison.  And apparently he finally found the treasure, then disappeared, then reappeared with a lot of money.

The bad guy is an abuser of women and McGee finds his last victim and helps her recover.  Then he goes after the man when he sees him isolating another woman, this time a young college girl and a floozy.