Season 5 Episode 21 - Meridian

SG1 returns from a visit to Kalowna with Daniel irradiated at a lethal dosage that will kill him in less then a day. In flashback the team relates how they met with an ethical advisor, Jonas Quinn, and witnesses the Kalownans' process for extracting a high-energy output naquadria to create a weapon. Then they reveal that Daniel was somehow irradiated and the Kalownans are accusing him of sabotaging their weapon program. Daniel says it was an accident and he's taking the blame for it. The Asgard and the Tok'ra are out of contact and Sam's attempt to use a Goa'uld healing device fails.

Jack is insistent that Daniel not be blamed despite the fact that SGC plans to not dispute the charges against him and try to maintain diplomatic relationships. Daniel has visions of Oma who encourages him to "ascend," while Jonas is inspired by Jack to steal some naquadria and bring it to SGC, while revealing the truth to his government - that Daniel sacrificed his life when a chain reaction threatened to destroy the entire planet. His revelation cuts him off from his own people, forcing him to remain at SGC. Jacob Carter arrives in time to try and cure Daniel, but Daniel asks him to stop. Resolving to take a new path, Daniel ascends and disappears.