Teal'c visits Atlantis to counsel a headstrong Ronon, who is up for review by the I.O.A. But the two must work together when the Wraith invade the Midway space station in order to reach Earth.

The Atlantis expedition has a plan to remove the Wraith's dependence on feeding to use an experimental gene therapy from Michael's database. However, in order to convince the Primary, the Wraith leader, Teyla Emmagan must pose as a Hive Queen.

Dr. Daniel Jackson arrives in Atlantis to investigate a hidden lab left behind by the rogue Ancient scientist Janus. Their discovery has attracted the attention of a mysterious group of aliens, who infiltrate the city. Meanwhile, "Todd" and a delegation arrive on the Daedalus to bring forward Dr. Jennifer Keller's gene therapy.

As Dr. Rodney McKay and Dr. Daniel Jackson is held prisoner by the Vanir, they make a startling discovery about who they really are. Meanwhile, "Todd" and his Wraith hijack the Daedalus to find and destroy those who activated the Attero device. The Travelers arrive and Lt. Colonel John Sheppard must help them get to the planet before "Todd" uncovers a way to discover the device for good, even if it means sacrificing McKay and Jackson's lives to do so.

Dr. Carson Beckett, now a traveling doctor in Pegasus comes across a planet, where some of the villagers are refugees from Balar, a planet infected with the Hoffan drug, and destroyed by the Wraith. However, the Wraith arrive on the planet and gives the village an ultimatum, hand over the Balarians, or face destruction of the entire civilization.