Showing Before I Say Good-Bye by Mary Higgins Clark

When Adam Cauliff's new cabin cruiser, the Cornelia II, blows up in a New York harbor with him and several close business associates aboard, his wife, Nell McDermott, is not only distraught at the loss but wracked with guilt because she and Adam had had a serious quarrel, and she had told him not to come home. As the investigation into the boat's explosion proceeds, Nell is shocked by the official confirmations that it was not an accident but foul play. Was Adam the target of the explosion? As Nell searches for the truth about Adam's death, she receives messages from Adam transmitted by a medium. What she doesn't know is that she is being closely watched, and the nearer she comes to learning what actually happened on the boat that night, the nearer she is to becoming the next victim of a ruthless killer.