Years before exorcising the devil from Regan MacNeil, Father Merrin (Stellan Skarsgård) experiences a crisis of faith, leaves the priesthood and heads to Africa on an archaeological expedition, where he unearths a perfectly preserved ancient church. The mysterious church, horrific events and the healing of a crippled boy (Billy Crawford) soon draw Merrin into a battle against pure evil in this creepy prequel to the 1973 horror classic.