Epiphany

"Epiphany" is the twelfth episode of the second season of Stargate: Atlantis.

Synopsis
Lt. Colonel John Sheppard is sucked through the event horizon of an entrance to a cave, and cannot get out the same way. Worse, there is a Time dilation field, meaning that minutes in relative conditions could mean hours for Sheppard. If they don't find a way to save him soon, he is going to die of old age.

Plot
While scouting a planet by Puddle Jumper, the team notices what appears to be a massive crater on the surface. Dr. Rodney McKay asks to check out the rim of the crater as he has detected energy readings, but once they get there, all they find is a doorway and some Ancient writing. However, the energy readings are coming from the doorway. Just to be safe, McKay ties a camcorder to the end of a stick and puts it through the door, discovering an energy barrier that it must pass through. He then pulls it out and deduces that the other side appears safe, allowing Lt. Colonel John Sheppard to pass through. A problem arises, however, when Sheppard is unable to pass back through the doorway, and suffers injuries from the stresses of the barrier. What is more troubling, though, is that time within the barrier seems to be passing much faster than time outside the barrier, which Rodney failed to realize until further review of the tape after Sheppard passed through. Sheppard could already be starving to death. McKay, Ronon Dex, and Teyla Emmagan 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.

Meanwhile, outside the barrier, only a few hours have passed and the team has returned. Although a probe sent through the field is destroyed, it locates the power source of the field and McKay also concludes that time in the field passes about 250 times faster than in real time, which would mean that a single hour in real time would equate to at least 10 days within the field.

Inside the field, Teer confidently responds that her lifetime of spiritual practice has given her clairvoyance. This power warns her that the beast will attack Sheppard's team. But this time he gets help from the villagers who have realized that the beast is only a manifestation of their fears. Now that they have realized this they all ascend – and although they extend an offer to join them, Sheppard declines. Teer then turns to McKay, advising that he not remove the ZPM, for it must remain for others to use. However, they will open the barrier for them to leave.