The Final Detail (Myron Bolitar #6) Harlan Coben

Myron Bolitar screwed up. He was supposed to be protecting a woman. Instead, he fell in love with her - and then she died. So he's dropped out and run away to the Caribbean to escape his guilt. But now everything has come back to haunt him.

Esperanza Diaz, his closest friend, is in trouble. Murder trouble. The victim is one of Myron's own clients, and the case seems to be watertight. It's inconceivable that Esperanza is involved, but she is refusing to deny it. So, in order to help his friend, Myron must battle for her freedom against her own wishes....