“The Ark” is episode sixteen of season three of Stargate: Atlantis.
Sheppard’s team discover a space station inside a small, hollowed out moon orbiting a planet with no intelligent life on it.
The station has been constructed using comparatively primitive technology that’s been combined with some Wraith technology in order to function as an ark in order to preserve the lives of some of the planet’s inhabitants from the Wraith. When the team accidentally revives a crew member, he loses control after discovering his family has not survived and kills himself – and tries to take everyone else with him in the bargain. His attempt to kill everyone else fails, but causes enough damage that they only have a limited amount of time before the moon burns up in the atmosphere. Bit of an oops that.
Quite a good standalone episode.