Several million years ago, in a beautiful alien city in Antarctica, a man and a woman in silver clothing — two of the Ancients who created the Stargates — look out a window sadly as the city rises out of the encroaching ice and flies away to the stars, leaving behind only a small outpost.

Present day: At the Ancients' abandoned outpost (discovered in the Stargate SG-1 episode "Lost City," Part 2), Dr. Elizabeth Weir, head of the Stargate Atlantis project, rides an elevator with Lt. Aiden Ford down a deep shaft bored in the ice. Reaching the research facility below, they find Dr. Rodney McKay and Dr. Carson Beckett arguing over the fact that Beckett is afraid to sit in the Ancient chair that controls the most powerful weapons known to humankind — even though he possesses (and is the one who discovered) the mutant gene to which Ancient technology automatically responds. As Weir points out, only a handful of people have the gene, and every time one of them sits in the chair they learn more about the Ancients.

Dr. Daniel Jackson of Stargate Command then tells Weir and McKay of a remarkable discovery he has just made: The stargate address to the lost city of Atlantis is incomplete. On a white board he adds an eighth symbol — indicating that Atlantis is not on Earth nor even in the Milky Way galaxy, but on a planet far, far away. And they can 'gate there.

As Gen. Jack O'Neill races to the outpost in a helicopter flown by Maj. John Sheppard, McKay convinces Beckett to sit in the chair. It activates and launches an Ancient drone weapon that almost destroys the helicopter. Thanks to Sheppard's fancy flying and Beckett's newfound ability to turn off his control, the chopper lands safely.

At the outpost, Daniel tells O'Neill that the Ancients flew their entire city to a dwarf galaxy called Pegasus. In order for an expedition to 'gate that far, they need to boost the stargate with the Earth's sole ZPM (zero-point module), an Ancient energy source that currently is powering the outpost's defenses and is vital to Earth's defense against an alien attack. The 'gating might totally drain the ZPM.

And even if it doesn't, there won't be enough power for the Atlantis team to 'gate back.

(continued)