This sequel to the 1994 movie Stargate chronicles the further adventures of SGC (Stargate Command). It turned out that the Goa'uld Ra was only one of many alien System Lords who used the Stargates to conquer much of the universe. When Earth uncovers a working cartouche to decipher the coding system of their own Stargate, they find they can now travel anywhere. Earth's military sends out SG teams to explore new planets, find technology, and oppose the Goa'uld. Jack O'Neill and Daniel Jackson from the original movie are part of SG-1. They are joined by Sam Carter, a scientist, and Teal'c, a Jaffa who is convinced the Goa'uld are not gods.
As the team embarks upon its tenth year, Vala, a former Goa'uld host turned freedom-fighter, joins SG-1 in their battle to defend the galaxy from the holy war of the Ori. Having discovered the existence of a weapon capable of defeating the Ori, the team is now in a race against time to find it before more systems fall to the influence of the Priors and the threat of the newly arrived Origin fleet. The season is continued with direct-to-DVD film Stargate: The Ark of Truth.
As one team member transitions into a new role, another is met with hesitation in season nine. Having learned of the Ori's plan to control the mortal plane, the team must find Merlin's secret weapon that may destroy the Ori and ensure the safety of Earth.