What is the Third Secret?

It is rumoured to be a prediction so shocking that it has been locked away for over eighty years. Could this be what is drawing Pope Clement XV to the Vatican archive, night after sleepless night?

When Father Colin Michener is sent on a secret mission to the highlands of Romania, he is pitched into a vortex of suspicion, deceit, murder and forbidden passion. Suddenly, he is forced to face the very thing that has so distressed the Pope - and to unravel a mystery that will shake the world.