Ep 3. Origin (3)

Vala Mal Doran, the former host of the Goa'uld known as Qetesh, seeks sanctuary at Stargate Command after barely escaping an Ori warship. She tells SG-1 that the Ori are planning on invading Earth, and are sending their religious followers, known as Priors, to convert the populations of planets they hope to conquer. One Prior, a former human now fully devoted to the Ori, has already landed in a nearby Colorado town, where he begins converting its residents. SG-1 attempts to capture the Prior, but he proves to be more powerful than they initially believed. Meanwhile, Dr. Carolyn Lam, the new head of the SGC's infirmary, examines Vala and discovers something alarming about her condition. As the episode progresses, SG-1 must confront the Ori threat which not only poses a physical danger but a threat to the beliefs of their members as well.