If you click on the cut below, you get spoilers. SPOILERS for this upcoming season 4 episode. Information is incomplete, and it's subject to change, but click if you don't mind big spoilers....
This is a Ronon-centric episode. Synopsis is derived from incomplete information.
Ronon discovers survivors from Sateda. TYRE, one of his former comrades (among others) hid in a network of caves on Sateda. Unfortunately, when the wraith attacked, they were sealed in the tunnels by a collapse and it was weeks before they could free themselves and escape.
TYRE and others are now nomadic, never staying in one place long. They know that Ronon is with the Atlantis crew (rumors abound in the Pegasus Galaxy), but, although Ronon wanted them to visit Atlantis, the welcome mat isn't exactly extended. TYRE thinks that's because Ronon is their ally, not necessarily their friend, and they'd like him to join them.
and........... that was in the beginning of the episode, and now we lose a chunk of time and head toward the end.......
Alas, we're now in a Wraith research facility of some kind where things just basically go to hell. Ronon discovers his friends are (insert music mostly used in horror movies) wraith worshippers! They were tortured by the wraith, brought nearly to an early death, then revived (much like Shep had done in COMMON GROUND) but, after multiple times of this being done, they caved in to the
dark side. And now, they'd like Ronon to join them. It's then that ARA tells Ronon that MARIKA and HEMI didn't die while on a run, they were killed because they woudln't cave in to the wraith.
Guest characters include TYRE, ARA, RAKAI and of course and some nasty Wraith (so far).