On a new planet, Sheppard, McKay, Teyla, and Ronon discover an intriguing portal in a mountainside: an opaque force field surrounded by Ancient text. After inserting a camera through the field to check for danger, Sheppard decides to enter the portal himself. The instant he begins, however, he feels terrible pain. His teammates struggle to pull him back out, but the portal inexorably sucks him through.
After Sheppard vanishes, McKay makes a chilling discovery: The camera, which was only inside the portal for a few minutes, recorded hours of footage. Time runs much more quickly on the other side of the barrier; Sheppard could already be starving to death. McKay, Ronon, and Teyla quickly toss all their supplies through the portal. Then McKay departs for Atlantis to get help - before Sheppard dies of old age.
Indeed, inside the portal, days have passed. Trapped in a cave without food, water, or word from his team, Sheppard is discouraged. The arrival of the supplies helps, but when more days pass with no further contact, he's forced to seek food elsewhere. He discovers that, on the other side of the immense mountain range above him, the cave opens into a verdant valley. Unexpectedly, a man races up to him, shouting frantically about a beast. Then the beast - a semi-invisible monster - attacks them both, knocking Sheppard unconscious.
He awakens in a tranquil village. The man, Avrid, and his sister, Teer, explain that the Ancients created this valley as a place for people to meditate on spiritual truths and, eventually, Ascend to a higher plane of existence. To Sheppard's horror, they add that, except by Ascending, no one can leave the valley. Ever.
Weeks turn into months as, with Teer's help, Sheppard struggles to adapt to his new life. Then, one day, the mysterious beast attacks the village. To Sheppard's disgust, the villagers hide, leaving him to face the creature alone. He barely survives. Feeling abandoned by his teammates and now by the passive villagers, the deeply frustrated Sheppard tries to make his new friends understand that Ascension won't mean much if they're mauled to death before they can achieve it. Teer confidently responds that her lifetime of spiritual practice has given her precognitive abilities. She has foreseen that Sheppard will defeat the beast and lead her people to Ascend.
Sheppard has serious doubts. He can't defeat the supernatural monster alone, and Ascension isn't really his thing. Luckily, though he doesn't know it, his teammates are on their way - with just one small catch: They could be years too late.