Close to the Bone - William G. Tapply

When a troubled friend disappears offshore, Boston lawyer Brady Coyne suspects foul play in "another winning entry in [this] very satisfying series" (Publishers Weekly).
Although alleged criminals are considered innocent until proven guilty, acquittal doesn't make them saints. Boston lawyer Brady Coyne knows this all too well, but believes firmly enough in the right to counsel that he doesn't let it keep him up at night. His friend Paul Cizek, however, is another story. A rising young defense lawyer, Paul has made a name defending repugnant clients: hit men, child molesters, unrepentant drunk drivers. He's good at what he does—so good that it's eating him alive.
After an emotional confession to Brady, Paul takes his boat out onto the Merrimack River in the middle of a storm. When the coast guard finds the vessel, the lawyer has vanished. Did he die in an accident, or did the stress of his work convince him to end it all? Brady suspects murder, and he will do whatever it takes to understand how his friend died.