As the Ori invade the Jaffa planet Chulak, Vala and Daniel must deal with their leader: Vala's young daughter, rapidly aged by the Ori to serve their purposes.
SG-1 investigates a problem off-world and soon finds that they have become victims themselves: they cannot stay awake. Meanwhile, Vala Mal Doran undergoes an evaluation on Earth, hoping to join SG-1.
Daniel and Vala travel to Atlantis in search of Merlin's anti-Ori weapon, while Sam, and Mitchell join forces with Dr. McKay to lock out the Ori supergate.
Teal'c discovers a world where people are being savagely attacked by an elusive creature, leading SG-1 to a stunning discovery about its potential origin.
SG-1 tries to defend a planet from the Ori by hiding its people in another dimension. Vala attempts to convince her husband Tomin of the Ori's true motives.
An experiment gone wrong pulls Samantha Carter into a parallel reality, where she must save Earth from an Ori assault before she will be allowed to return home.
When SG-1 discovers that Daniel Jackson has been turned into a Prior of the Ori, they must determine whether or not his plan to destroy the Ori is genuine.
SG-1 realizes they have stepped through the gate into another planet's museum -- but are mistaken for a band of zealous rebels who have taken hostages.