The Fourth Horseman
Season 9, episode 10 of Stargate SG·1 (1997) · 2005-09-16
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Episode Summary
After an SGC officer returns to Earth after unknowingly being infected with the Ancient Plague, the virus quickly spreads throughout the United States. Not wanting the Ori to gain control of the Milky Way Galaxy, Orlin yet again descends to help Carter find a cure.