When Old Men Die — Bill Crider

Truman Smith is happily fishing off a Galveston pier when his friend Dino seeks him out and asks for some help: Outside Harry, an old-timer with connections to Dino's family, is missing.
Smith doesn't want to have anything to do with it; the last time he looked for a missing person the outcome left something to be desired. But Dino has a way of being persuasive, and Tru promises to give it a day or two.
When the first person he questions is murdered, and when he himself is shot at, Truman Smith is reminded of all the reasons he hates missing person cases. But he's committed now: Outside Harry's life is in his hands, and Smith is going to see to it that if Harry has any secrets he wants to tell, he won't have to take them to an early grave.