History professor Dan Harrington and Sister Frankie Latrobe, a feisty African-American nun, uncover allegations of child abuse involving Pope Clement XV. Liberal Archbishop Mark Doyle, a continuing thorn for the Vatican for his liberal ideas and a romantic relationship that produced a love child, joins Dan and Frankie to their search for evidence.
Their investigation takes them to Frankfurt where Pope Clement taught in the mid-seventies. Leads uncover a middle-aged brother and sister from a prominent German family who claim to have been abused as teens by the man who is now Pope.
With support from Mark, Dan, and Frankie, the siblings go public, provoking an explosion of worldwide publicity. A right-wing Catholic group, Ordo Novus, traces the Archbishop's connection to the child abuse controversy, and stalks Mark, Dan, and Frankie in order to shut them up.
Pressure mounts on the Pope, as demonstrations around the Vatican and elsewhere intensify, calling for him to resign. Clement wrestles with his conscience and chooses a drastic action to solve his dilemma.