There is often the look of an angel on the Devil himself – old Irish expression.

When a statue of the Virgin Mary in a Lourdes grotto outside a small village in rural Ireland begins to move, the countryside is plunged into a fever of religious mania. Thousands ― the faithful, the sceptical, the merely curious ― flock to Loughermore every night to see Our Lady smile, open her eyes, hover or shed tears, but not everybody leaves the grotto in the throes of religious ecstasy; after experiencing sheer terror at the foot of the statue while witnessing its transformation into a diabolical figure, Brian McNamara begins to suspect that something malevolent is lurking within the stone. Upon further investigation, Mac and his friends become convinced of the presence of a demon-like entity within the statue, something that is feeding off the adoration of the unsuspecting masses and capable of compelling those that come under Its thrall to engage in the most vile and depraved acts of violence. They discover that six pillars of the community calling themselves the "Guardians" are acting as the entity's agents and are responsible for a spate of ritualistic animal mutilations in the locality. The friends immerse themselves in the world of demonology and Celtic mythology and trace the entity's origins to Ireland's mysterious megalithic past. As they learn how to harness the ancient power of stone circles to subdue the entity, it becomes a race against time to stop the Guardians, who have embarked upon a series of brutal murders and dismemberments — blood sacrifices the entity requires in order to be able to assume physical form and escape from its stony prison within the statue.