Could you clarify which show you are looking for a deep dive on? Here are the most likely candidates:
:This episode is actually titled "Beware the Jabberwock, My Son," but it deals with a high-stakes "enemy within" plot involving a supe-killing virus and the return of Stan Edgar. [S4E5] Enemy at the Gates
: 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 " ). Could you clarify which show you are looking