Book of Q

After the mysterious death of one Vatican priest and the disappearance of
another, Father Ian Pearse, an American working on early Christian texts
in the Vatican, comes into possession of a mysterious scroll. He
discovers ingeniously coded letters and the text of an ancient prayer never before found in written form.

These reveal a conspiracy, by a sect long-thought dead, reaching deep
into the present Vatican hierarchy.

It becomes a race against a ruthless unknown opponent, which takes
Father Pearse from the Vatican, via an ancient Greek monastery, to war-
torn Bosnia.