Teri McIntyre has enrolled her 15-year-old son at St Isaac's Catholic boarding school, hoping this venerable institution will have a calming influence on him. But Ryan arrives to find the school awash with rumours of violent death, mysterious disappearances, and a growing incidence of disturbing behavior within its hallowed halls.

Things begin to change after Father Sebastian joins the faculty, bent on an extraordinary mission to prove the power of exorcism. Willing or not, St. Isaac's most troubled students become pawns in Father Sebastian's one-man war against evil -- a war so surprisingly effective that Rome itself starts taking notice.

But as Ryan is drawn ever more deeply into Father Sebastian's ministrations, he witnesses with mounting dread the transformations of his fellow pupils, and his certainty grows that it is forces of darkness, not divinity, which are at work here. For evil is not being cast out ... instead, something unholy is being summoned. Something whose hour has finally come to bring hell unto earth.