Stargate Atlantis: Season 2, Episode 12

2 - 12: Epiphany

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.