SG-1 arrives on a planet where a culturally 'medieval Catholic' community lives in fear of an Unas they believe to be a demon, which regularly collects human sacrifices to Satan - in fact hosts for System Lord Sokar's army. When Simon implores SG-1 to spare his beloved Mary and take him instead, they even nurse her chicken pox. Simon hopes they are sent by God to deliver them from the satanic burden, but the canon who rules the village as 'spiritual' leader is faithful to Sokar and fears his authority, which rests on his right to select the 'damned soul' to be sacrificed, has been challenged, so he declares Teal'c a demon and incarcerates all SG-1. Witch-trial-type ordeals see the Jaffa 'proven' a demon and executed by drowning, and Daniel refuses the canon's warning to leave immediately. When Teal'c's symbiote allows a resurrection even Sam hadn't expected, they are all designated possessed and sacrificed, along with Mary. Simon follows the Unas with a staff weapon to liberate them, but he's not alone.