Stargate: Atlantis Episode 5.12 Outsiders

Col. Sheppard and his team locate Dr. Beckett on an alien planet where he is treating a small group of survivors of the Hoffan plague. These patients, who escaped a Wraith attack on their home world, Balar, have found sanctuary and friendship on this alien planet. But that same evening, a party of Wraith warriors appears before the village's councilors, demanding that the refugees be turned over to them, threatening total annihilation if they refuse.

The Balarians, aware that they are not only immune, but lethal to a Wraith, fear there is no chance the townspeople will continue to harbor them. And they may be right. Despite Sheppard's best efforts, it appears that the original residents intend to sacrifice the newcomers in order to save themselves.