The episode opens in the briefing room, with Daniel giving everyone information about a recent probe and its photos of a bunch of symbols that matched the symbols on a pedestal on planet PB2-908. After some convincing by Daniel, the team gets the okay to go out investigate.
While on planet P3R-272, SG-1 comes across an Ancient device that protrudes out of the wall of an underground room. The room is cylinder shaped, dark blue walls with nothing but a white beam of light coming down from somewhere above. Teal'c looks into the object and sees blackness, with colorful lights. He steps back and Jack decides to take a look himself. Jack looks into the device and notices that the colors and lights seem to respond to him. The device changes shape and he sticks his head back cautiously, but immediately the device reaches out and grabs his head, forcing him to witness a bright probing of light. He is knocked unconscious and taken back to SGC for observation.
The doctor release him after testing his vitals, and all is seemingly back to normal. Jack hops up from the medical desk: "Don't remember a thing"
In the debriefing, Hammond is asking questions about the incident, and Jack seems irritated about the entire situation. Everyone asks him is he okay, and he states that he is, but accidentally says "cruvus" instead of worried. Jack has no memory of saying this, and after a bit of arguing, then simmering down, Hammond tells him to get some rest, but to stay on base. Jack has no problem with this and he decides to unwind with a little bit of boxing with Teal'c. Jack and Teal'c are in the gym with boxing gloves on and Jack is trying to teach Teal'c to move like a boxer, to dance around a bit. Teal'c is confused and questions Jack if they are going to box or dance? Jack tells him he is a sitting target if he does not move, and punches Teal'c in the chest. Teal'c looks unbothered by this small, weak punch, and Jack is suckered punched in the face when he lets his guards down to try to explain again. Jack gets up and tries to make sure his nose isn't bleeding and tells Teal'c he has to keep his hands up, and to "Bend your cosars" Teal'c notices this error and tries to correct Jack, but Jack repeats "cosars" instead of legs, as if there wasn't anything wrong. Teal'c is able to make Jack realize that he is using a different word, and now Jack makes his way to Daniel for help in figuring out what is wrong with him.
In Daniel's lab, Jack waits for Daniel to define "falatus" and sees text written in Ancient on a computer monitor. Jack begins to read it, and Daniel, surprised, rushes over and asks Jack if he's reading that. Jack doesn't know, he just knows that he sees it and the words are popping into his head.
Jack is given a brain scan, and it is revealed that his brain is using over 90% of its capacity. Hammond and Samantha are worried about what could have caused this, but Daniel is able to discern that what grabbed him was actually some type of library that downloaded ancient knowledge directly into his mind.
Jack, soon after, begins doing thing he doesn't know why he's doing it. He begins taken small parts from devices, and goes to SGC where he writes a program that inputs unknown gate coordinates into the computer. Jack is not allowed to touch a computer anymore after this, so says Hammond, and he is taken back to Daniel's lab to help Daniel translate more of the Ancient's text. While helping Daniel, Jack translates text that leads Daniel to believe that the Ancients were the original gate builders. He also comes up with a revolutionary formula for calculating planetary drift between Stargates.
Later, a new planet is found to have markings that are Ancient, and Teal'c and Sam are tasked investigating while Daniel and Jack do more translating. Jack is getting impatient, and tells Daniel he has to go somewhere, he just doesn't know where. Back on the planet, Sam tells Hammond and SGC that the dial home device is broken, and there is another sun that the MALP missed that could cause the temperature to rise above 200 degrees. Jack is finishing up his little invention that he'd been piecing together for awhile, and cuts it on when done with the doctor and Daniel present. It does nothing, and he still doesn't know what it is.
Back on the planet, Sam and Teal'c are in trouble. Hammond tells them of counter measures being made to help them through the heat, but Sam knows it's not enough. Jack is told of their situation and draws plans up for them to fix the Stargate on their end. Soon after, he sends them through the wormhole in time to save his teammates.
After a break, the Stargate gets frozen when they try to connect to one of the new addresses that Jack entered into the computer. The system needs more power than can be provided, and Jack springs into action with his invention and takes it to the power room. Jack, no longer able to communicate at all with the others, hooks it up to the main breaker and there is an outstanding boost of energy that allows the wormhole to connect.
Jack needs to go through, and Daniel knows this, everything led to this moment. Jack seems lost, his mind no longer in SGC, and Hammond allows him to go through the Stargate.
On the other side Jack pops out and is confronted by Asgard. They take the information out of his head, and he passes out, but wakes a few moments later. He thanks them, and they talk about the four races that formed an alliance many years ago. The Asgard are surprised Jack's brain could handle that much information, and Jack makes a plea for the Asgard not to look down on humans or their matters anymore. Jack is offered a hand of friendship, and the episode ends with a welcoming of Jack and humans to the Asgard, and the possibility of becoming the Fifth Race.