King Lear is perhaps the most fierce and moving play ever written. And yet there is a curious puzzle at its center. The figure to whom Shakespeare gives more lines than anyone except the king--Edgar--has often seemed little more than a blank, ignored and unloved, a belated moralizer who, try as he may, can never truly speak to the play's savaged heart. He saves his blinded father from suicide, but even this act of care is shadowed by suspicions of...