SG-1 arrives at a medieval village and frees Mary, a young woman who has been left outside tied to a stake. Simon, friar of the village and Mary's friend, explains that Mary is a sacrifice for the demon that plagues their village. The Canon chose her when he mistook her illness for an evil possession.
When the demon arrives and finds no sacrifice, he promises to destroy the village the next day unless five humans are left for sacrifice. SG-1 recognizes this "demon" and plot to destroy it, but the Canon pronounces SG-1 evil and condemns them to be sacrificed.
SG-1 must convince Simon to go against everything he believes in order to save themselves and rid the village of their demon forever