On the day she died, Constance Young was the undisputed star of morning television. But her plans to move herself and her loyal audience to another network were cancelled when she ended up at the bottom of her swimming pool. And the fabled unicorn amulet that Constance had been wearing during her final hours-a gift from King Arthur to his beloved Guinevere and the centerpiece of the upcoming Camelot exhibit at New York's Cloisters museum-is missing. A...