The following story contains MODERATE SPOILERS for the upcoming third season of "Stargate: Atlantis."

The third season of "Stargate: Atlantis" will conclude with an episode titled "First Strike," written by Martin Gero and directed by Martin Wood, according to the GateWorld website that also released plot details.

A new ship has arrived in Atlantis from Earth: the Apollo, commanded by the brusque and take-charge military officer Colonel Abe Ellis (possibly a recurring character next season). Ever since the human-form Replicators tried to seize Atlantis, the Daedalus has been doing reconnaissance fly-bys over their homeworld. And they've found something, GateWorld said.

Ellis tells Dr. Weir, Col. Sheppard and Dr. McKay that the Replicators are building a fleet of ships. Presumably, the technologically advanced strike force is coming to Atlantis, to reconquer the city that the artificial lifeforms were forced by their creators, the Ancients, to leave thousands of years ago. Either that, or they may come to Earth, of which they now know the location, according to the GateWorld synopsis.

But, Ellis says, he has been sent to command a strategic first strike against them. Because these Replicators appear to build their ships out of standard materials rather than forming them out of Replicator cells (as did the Replicators in our home galaxy) they can be destroyed the old fashioned way, GateWorld said.

Meanwhile, McKay reports, the Asgard have created a satellite weapons system that can wipe out an entire planet populated with Replicators. Area 51 is trying to do the same thing, the synopsis said.

But Elizabeth Weir is gravely concerned about the mission. Even if it is a great success, they will be starting a war -- a war against a very powerful enemy. And she will have to take drastic measures in order to save the city of Atlantis, GateWorld said.

"First Strike" will be filmed in late September and early October, and is expected to premiere on the SciFi Channel in the U.S. in June.