The past year has given us two searing portraits of the human crisis in Darfur: Darfur Now and The Devil Came on Horseback. Tonight on HBO, a worthy third film joins them. In Sand and Sorrow, director Paul Freedman and narrator George Clooney follow John Prendergast, Samantha Power and Nicholas Kristof as they explore the tragedy of the genocide in Sudan. They journey through refugee camps on the Chad-Sudan border, visit mass graves inside......