.O'Neill, being happy that they have saved the planet again, plans a relaxing fishing trip to Minnesota. However, SG-1 is once again called into action, as at least one Replicator has survived Thor's spaceship's crash into Earth's ocean. A Russian sub has reported being attacked by metal bugs just before contact with the sub is lost. Thor makes a reappearance to thank the team, but he also tells them the Asgard are continued to be greatly threaten by the Replicators at the moment. Carter agrees to go with Thor to help the Asgard try to defeat the Replicators attack, hoping to use, as the Asgard call it, her earthling primitive ideas. At the same time, O'Neill and Teal'c rush to the Russian sub, now under US control, to see if they can stop the Replicators from gaining a foothold on Earth. If either team fails, the Earth will be doomed to be overrun by the Replicators.
Season 4 Episode 1 of Stargate SG-1 resulted in a 0.00 rating in the 18-49 demographic.
Step through the Stargate with SG-1, a team of soldiers and scientists, as they travel instantaneously to other planets to explore, forge alliances, defuse crises, establish trade, investigate ancient mysteries and defend Earth from such hostile forces as the Goa'uld and the Replicators.
For eight years, from their base at the U.S. Air Force's Stargate Command in the Rocky Mountains, Colonel Jack O'Neill, Dr. Daniel Jackson, Lt. Colonel Samantha Carter and alien warrior Teal'c have braved everything that the universe has thrown at them, from interstellar war and evil twins to death and ascension.
But changes came to SG-1 as it began its ninth year of fearless service to Earth. New faces joined the team, as Lt. Col. Cameron Mitchell tries to fill the very big shoes of former SG-1 leader O'Neill, while General Hank Landry must adapt to the unique challenges of running Stargate Command, a posting unlike any other the military has to offer.
Offworld, SG-1 might have new friends - or new foes - in Vala, a former Goa'uld host turned freedom-fighter; and Gerak, a Jaffa leader who vies with Teal'c for political control of the new Jaffa nation.