Ep 6. Beachhead

SG-1 returns to Earth after a dangerous mission only to find that the Stargate has been sealed off. General Landry informs them that the Stargate Program has been shut down due to political pressure. Meanwhile, an unstoppable alien warrior named the Prior arrives on Earth. He claims to have been sent by the Ori, a powerful and malevolent civilization worshipped as gods by many civilizations in the universe. The Prior demands that the people of Earth embrace the teachings of the Ori or face annihilation.

SG-1 investigates and discovers that the Prior has set up a beachhead on Earth, a mysterious device that is continually generating a powerful energy field. Anyone who enters the field is rendered unconscious and is unable to leave. The team realizes that the Prior plans to use the beachhead to open a wormhole to his home planet, allowing the Ori to launch a full-scale invasion of Earth.

With the Stargate Program shut down, SG-1 must find a way to stop the Prior and shut down the beachhead before it's too late. They seek the help of Vala Mal Doran, a former antagonist and thief who had joined their team in a previous season. Vala uses her connections to the criminal underworld to acquire a specialized device that can disrupt the energy field of the beachhead.

SG-1 then devises a plan to infiltrate the beachhead using a specially-modified aircraft. They succeed in attaching the device but are forced to battle the Prior and his army of followers. The team manages to hold them off long enough for the device to take effect and shut down the beachhead, preventing the Ori invasion.

As the team returns to Earth, General Landry reveals that he has managed to convince the government to unseal the Stargate and reactivate the program. SG-1 is once again able to travel through the Stargate, opening up a whole new universe of adventure and danger.