Dark Harbor by Stuart Woods

When Stone Barrington's cousin, Dick Stone, dies and leaves everything pretty much in Stone's hands and omitting Dick's brother from his will, all heck breaks loose. Originally considered a double murder, suicide death, clues lead Stone to believe that all three members of Dick's family were murdered. Natives of the island in Penobscot Bay feel threatened when young women begin to be assaulted and murdered. Stone calls in friends from home including Lance and Holly from the CIA and close friend Dino, police investigator. A group called the "Old Farts" and friends, former work acquaintances of Dick also think there is more to the mystery than everyone is seeing. Woods writes a twisted tale of family secrets and serial murders.