Colonel John Sheppard and his team are called off-world and arrive on a planet where Dr. Peel, a member of the Atlantis expedition, leads them hurriedly down a long alley. She was with Major Lorne's team, and when a routine mission to make contact with the seemingly friendly locals went bad he ordered her to return to the gate and call for backup. Upon returning to the home they were visiting for tea with the locals, Peel sees that it has been incinerated.

Details are sketchy, but it appears as though Major Lorne and his team have been captured -- by the Genii. Peel had heard what sounded like Wraith blasts, but she can't be sure.

Back on Atlantis, Dr. Weir is paid a visit by Ladon (Ryan Robbins), the young Genii officer who helped a Genii strike force capture the Ancient city more than a year ago ("The Storm" / "The Eye"). Weir wants a Zero Point Module from him -- and it could be Atlantis's own. Ladon wants to negotiate a trade for supplies.

Later, Ladon sends a team of 12 emmissaries to Atlantis for negotiations, including his own sister, Dahlia Radim. She is only in her 20s, but it soon becomes clear that she is dying. Dr. Beckett tries his best to help but Dahlia is less than cooperative, still regarding the expedition as her enemy and preferring to die in the course of doing her duty, to ensure that her family and friends have a home.

On planet M6R-867 Sheppard leads a strike force, possibly in an attempt to rescue Lorne and his team or to recover the Z.P.M. But he is captured, and again comes face-to-face with Ladon and the leader of the Genii, Cowen (Colm Meaney). There Sheppard learns that the Genii are attempting to seize control of a fleet of Puddle Jumpers, still intent on attacking Wraith hive ships with their nuclear weapons -- a strategy for suicide missions that they learned from Dr. Weir herself ("The Siege, Part 2").

Guest characters include Cowen (Star Trek's Colm Meaney will presumably reprise his role), Dahlia Radim, Dr. Peel, Ladon, a technician, and a security team member.

"Coup D'etat" is expected to go before cameras next month as the eighteenth episode in Atlantis's production order. It will air early in 2006 in the U.S.