While searching for the Lost City of the Ancients on a distant planet, SG-1 is stunned to find Daniel Jackson alive and in human form but stripped of his memory. O'Neill convinces Daniel to return with them to the SGC, where he is reinstated for a daring mission to destroy Anubis' powerful new super-weapon!
As SG-1 searches for an Ancient artifact which they hope can defeat the armies of the Ori, they learn more Ori ships are about to be sent through the Supergate to launch a final assault on Earth. Daniel discovers that the artifact, the Ark of Truth, may be in the Ori home galaxy, and SG-1 embarks aboard the Odyssey to find it, and pre-empt the attack. The IOA has a plan of their own and SG-1 ends up in a distant galaxy fighting two powerful enemies.