While exploring a new system, Maj. Sheppard, Teyla, Lt. Ford and Dr. McKay's puddle jumper falls under fire by two Wraith Darts. Weapons are knocked offline. Two more darts appear. The jumper's in serious trouble. Suddenly, a wave of energy emanates from the planet below. The Darts are destroyed, but the jumper is undamaged. McKay insists that the only power source capable of generating such an energy field is a zero-point module, which the Atlantis team desperately needs. They set down on the planet and find a pre-technological civilization.
Zarah, a peaceful-looking man in monk's robes, greets them. He is one of the Abbots of Proculus. Upon hearing Sheppard's account of their adventure, Zarah is convinced that they were spared by their goddess, Athar. Neither he nor his people have ever heard of the Wraith, which, in the Pegasus galaxy, is impossible. The only explanation is that these people don't know that an Ancient weapon exists on this planet that keeps the Wraith away. If the Atlantis team can negotiate a treaty with these people, this planet could become a sanctuary for many thousands of people who would otherwise fall prey to the Wraith.
Chaya turns into slivers of energy and passes through the gate. Sheppard pilots a jumper to Proculus to help her defend her people. Suddenly, Chaya materializes in the co-pilot chair, impressed that Sheppard has come to her rescue. But there was no need. She becomes pure energy again and wipes out the Wraith assault in an instant.
Sheppard lands the jumper on Proculus, where he confronts Chaya to learn the truth. She is Athar. There is no weapon. Chaya is one of the ascended Ancients. Because she defied their most sacred rule to not interfere in mortal matters and once saved her native people from the Wraith with a single thought, her punishment is to forever protect Proculus. But she cannot protect others, which is why she can't give sanctuary to the Atlantians or to Teyla's people. The ascended others would stop her.
She can, however, "share" herself with Sheppard. She holds his hands as an energy wave sweeps around them.