One False Step (S02E19)

During a simple reconnaissance mission, the UAV plane crashes into a cactuslike plant on a planet inhabited by an unusual life-form. Sent to recover the plane, the SG-1 team discovers those living on the planet are friendly, gentle and far simpler than their human counterparts. Shortly after the team's arrival, the aliens begin falling ill. Before long a plague of illness sweeps the race. Capt. Samantha Carter returns to Stargate Command with the sickest alien, in order to search for a cure. Meanwhile, Col. Jack O'Neill and Dr. Daniel Jackson begin acting erratically and complain of headaches that disappear once they are back at SGC. As the number of afflicted aliens grows, it appears that the SG-1 team has unwittingly unleashed something that threatens the survival of an entire civilization. (Metro-Goldwyn-Mayer (MGM))