“Vegas” is episode nineteen of season five of Stargate: Atlantis.
Sheppard is, in a parallel universe, a detective working in Las Vegas hunting down a serial killer. CSI: Crime Scene Investigation much? He’s not the only alternate in this universe, although the others still seem to have their original job.
The initial question is why would they be doing an alternate universe story set in Vegas? There does seem to be an actual point though as the victims have all had the life sucked out of them. It turns out that there’s a Wraith in Las Vegas, who’s disguising himself as a human. He ended up on Earth after a Wraith hiveship was defeated.
Rodney is still with the Atlantis team, and has met another version of Sheppard, when he went through a dimensional rift, and Todd the Wraith – or his alternate – is in captivity.
Yes, there are Wraith and Atlantis in this episode, but it was difficult to see the point for some time, but it seems that what happened will apparently cause a problem in the main universe.