The inhabitants of P3X-289 are suffering the effects of planet wide inhospitably. To survive the harsh environment, they built a dome, controlled by a machine known as the Link. The Link also contained the knowledge of the world, and was made accessible via a device to the population. However, when the dome started losing power, the Link used its influence on the people to force them to step outside the dome, killing them, and then rewrote the memories of all the people, so they didn't realise what had happened. SG1 came to the planet realised what happened, and saved the remaining inhabitants, which had gone down from over 100,000 to a few thousand.