William Darnell thought he had seen every kind of human conflict, every type of human tragedy, seen them in all their immense variety: murder done from envy, murder done for revenge, murder done for money, murder done for love, murder done after careful planning, murder done in a moment's rage. He had known, and defended, every kind of murderer, all of them, despite their differences, driven by the same desire, known since Cain slew Abel: the need...