In this action-packed thriller, a Harvard theology professor uncovers religious and papal history—and plenty of conspiracy.   Cal Donovan, a theology professor at Harvard, receives an urgent message from a former graduate student, Samia Tedros. Now a museum conservator in Cairo, Samia has discovered a miraculous fragment of papyrus with three unknown lines from the Gospel of Mary Magdalene so explosive that a wealthy man is willing to kill to ensure no one ever sees it.   At