Season synopsis
Contains spoilers for this season and earlier seasons.
Season five opens with SG-1 and Apophis’s mothership stranded far from Earth after the Vorash supernova. The team boards Apophis’s abandoned ship, where Replicators have triggered its self-destruct; after escaping, they recover Teal’c, whom the sarcophagus has returned to Apophis’s service in his own mind. Replicators subsequently infest SG-1’s own mothership, which crashes on Delmak, leaving Apophis presumed dead, and Bra’tac’s M’al Sharran rite restores Teal’c’s memories and his choice to serve with SG-1. A warning note from a possible 2010 future makes SG-1 suspicious of its proposed Aschen alliance. On a Volian world, Daniel and Teal’c find a buried city and learn that an Aschen vaccine caused population collapse through sterility. The season also follows Russian involvement with the Stargate, uneasy Tok’ra cooperation, and a Jaffa rebellion whose leader proves less trustworthy than his cause first suggests.
The season’s most lasting change comes on Langara, where Daniel Jackson is exposed to lethal radiation while trying to stop a naquadria reactor disaster. Jonas Quinn, who has concealed the truth about Daniel’s actions, finally speaks up and leaves his world with a sample of the mineral; Daniel chooses ascension with Oma Desala and dies among his friends. In the finale, the Asgard ask SG-1 to rescue scientist Heimdall, and the team discovers that Thor is alive aboard an enemy ship. Anubis, a newly revealed Goa’uld power with advanced technology, tries to extract Asgard knowledge. SG-1 and Thor escape when the Asgard arrive in force, while an unexplained breeze suggests Daniel may still be near his former teammates.