: Are you thinking of the series finale, "Enemy at the Gate" ? Technically, this is Season 5, Episode 20 , but it’s the definitive "Enemy" episode for the franchise, featuring the final showdown between the Wraith and Earth. (Season 4, Episode 5 of Atlantis is actually titled " Travelers " ).
It looks like there’s a bit of a mix-up with episode titles and numbers across different shows! The phrase "Enemy at the Gate" is a very famous title, but it matches a few different iconic series in slightly different ways. [S4E5] Enemy at the Gates
Could you clarify which show you are looking for a deep dive on? Here are the most likely candidates: : Are you thinking of the series finale, "Enemy at the Gate"