Dr. Daniel Jackson makes an amazing discovery while translating the Ancient writing on the colonnade that SG-2 discovered on planet P3X-439. The writing talks about a library of knowledge and Daniel suspects it contains a repository - the same type of device that once downloaded the Ancients' knowledge into Col. O'Neill's brain and would have cost O'Neill his life had not the Asgard intervened and removed the alien data from his mind. However SG-2 spots a Goa'uld reconnaissance drone while on the planet which means that system lord Anubis is also aware of the repository's existence. SG-1 must get to it first so that they can once and for all learn the location of the Lost City of the Ancients and use that race's advanced technology to save the galaxy from Goa'uld oppression. Should this knowledge fall into Anubis' hands nothing will be able to stop him. This time SG-1's plan is to remove the repository rather than downloading it into a human and then to bring it back to Earth and find a safe way to retrieve the data. The Asgard and other alien allies are not responding so Stargate Command is on its own. SG-1 SG-2 and SG-3 are dispatched to P3X-439 where Daniel and Maj. Carter try to remove the repository from the monument - with no luck. Suddenly a full-scale Goa'uld attack rocks the monument as Alkesh fighters carpet-bomb the area. There is no choice: Someone must download the Ancient knowledge into his or her brain. O'Neill assesses that Carter is too valuable and that Daniel will be needed to translate the Ancient language that whoever goes through with this will be speaking when their consciousness is taken over and replaced by that of the Ancients - resulting in neural overload and death. So he does it again: O'Neill steps up to the repository where the face-hugging arms come out grab O'Neill's head and pump Ancient knowledge directly into his brain. The teams return to Stargate Command where they must face the inevitable: O'Neill's human consciousness will soon be obliterated and he will begin speaking in Ancient. Not long after that his human physiology will no longer be able to handle the strain and he will die.