The Goa'uld invasion of Alternate Earth was an invasion of Earth in an alternate reality led by the Goa'uld System Lord Apophis.
Prelude[]
Two Carters.
An alternate reality Dr. Samantha Carter and Major Charles Kawalsky flee their reality to ours using the Quantum Mirror. There they ask for sanctuary from their world as it has been overrun by the Goa'uld System Lord Apophis. While they are originally allowed to stay, Dr. Carter begins to experience entropic cascade failure due to the presence of two Samantha Carters in one reality and in order to prevent her death, SG-1 must free her world from the Goa'uld. They decide to contact the Asgard of her world for help and the two Carters are able to make the power booster device Colonel Jack O'Neill made while the Repository of knowledge was in his brain work again so they can dial the Asgard galaxy.[3]
Battle[]
Apophis tortures Major General George S. Hammond.
After Dr. Daniel Jackson finds the right reality in the mirror, Dr. Carter, Kawalsky, O'Neill, Teal'c and Jackson travel there while Major Samantha Carter from the correct reality remains behind. Once they arrive, they are forced to deactivate the mirror to prevent detection. Following the Jaffa, they find Apophis himself arriving through the Stargate and catch the alternate Teal'c's attention and lead him back to the storage closet where the mirror is. While Teal'c tries to get the alternate Teal'c to join them, he believes in the Goa'uld and Teal'c is forced to kill his alternate self. Teal'c then takes on alternate Teal'c's role as Apophis' First Prime and leads Dr. Carter to the Stargate Operations room where Apophis is torturing Major General George S. Hammond for the Stargate address to the Beta Site. Teal'c pretends to take over the interrogation as Apophis leaves and sends the other Jaffa with him. As they start to set up to dial the Asgard homeworld, a Goa'uld Ha'tak lands on top of Cheyenne Mountain. Teal'c and Dr. Carter are able to successfully set up the new dialing program created by O'Neill while he had the knowledge of the Ancients and O'Neill sets up the generator in the power room, causing the Stargate to dial the Asgard homeworld. As Hammond pretends to be a prisoner, Teal'c distracts a Jaffa that goes after Dr. Carter, allowing her to escape through the Stargate.
However, as a result, Apophis becomes aware of Teal'c's betrayal and captures Teal'c and Hammond. Returning to the storage closet, O'Neill and Kawalsky find Jackson captured and are forced to surrender to spare his life. They are taken before Apophis who threatens Hammond's life to force them to tell him how O'Neill is alive, having been killed in that reality and who Teal'c is. When Apophis doesn't believe them, he has Hammond killed. However, before Jackson can be shot more than once with a Zat'nik'tel, an Asgard mothership arrives and Apophis orders his troops to flee through the Stargate. As he goes to kill the prisoners, the mothership beams him and two Jaffa with him away and the Ha'tak retreats. Apophis' remaining Jaffa retreat through the Stargate and the invasion ends. The Asgard also beam away the alternate Hammond briefly and return him resurrected along with Dr. Carter.[3]
Aftermath[]
In the aftermath, with the alternate Earth saved, O'Neill, Jackson and Teal'c return home where their Major General George S. Hammond has the mirror destroyed.[3]