Mitchell, Carter and Teal'c arrive on a planet being threatened by the Ori. They decide that a line needs to be drawn and that the Ori must not be allowed to advance any further. Carter attempts to use the Ancient Merlin's technology to prevent the Ori from taking over the planet.

The SG-1 team learns of yet another world that has been visited by a Prior of the Ori. However, this Prior hasn't issued any threats. The team waits for the Prior's return, only to be shocked by his identity.