An alternate reality version of Samantha and Kawalsky show up at the SGC. They say they were under attack by the Goa'uld and went through the mirror trying to find an alternate reality where they could get help to defeat the Goa'uld. Dr. Fraiser confirms by a DNA exam that they are who they claim to be. They are all a little suspicious about this, but decide to give them a chance, since Daniel went through a similar experience a year before.
Dr. Carter and Major Kawalsky ask Gen. Hammond if it is possible for them to stay in this reality, since in their reality Earth is ruled by the Goa'uld and most of the other ones they looked through were too. Gen. Hammond says he will take their request under advice. After a few phone calls Gen. Hammond gets the permission for Dr. Carter and Major Kawalsky to stay, and Jack offers to give them the good news.
Jack goes talk to Dr. Carter and she tells him that in her reality they were married, and he died in her arms, trying to protect them from an attack. He tries to comfort her for a while. Latter when she is alone in her room, Dr. Carter starts to have some sort of a seizure and is rushed to the infirmary. Major Carter and everyone else rush to get there and try to figure out what is happening. Dr. Carter says it is a side-effect from being on the same reality as Major Carter, and they realize they cannot both stay in the same reality.
Daniel says they have to try to stop the Goa'uld attack in the reality they came from and send Dr. Carter and Major Kawalsky back. He says that maybe they can go to that reality and try to contact the Asgard to ask for help. Kawalsky asks to join in the mission and so does Teal'c, since in the other reality he is still the Apophis's First Prime and can infiltrate on the enemy lines.
Both Carters work together to make the device Jack built some time before work again while Kawalsky shows Daniel how to use the quantum mirror. Jack, Teal'c, Kawalsky, alternate Carter and Daniel go through the mirror and move on with their plan. They take evil Teal'c down and exchange him for SG1 Teal'c. He pretends to have found Carter hiding and takes her to the gate command room. While Daniel guards the mirror and tries to find their reality again, O' Neill and Kawalsky go put the device in place.
Apophis is torturing the Hammond from this reality when Teal'c comes in with Carter, he orders Teal'c to get the address to the beta site from one of them using any means necessary. As soon as Teal'c is left alone with the prisoners, he frees Hammond and helps Carter set up the computers to dial to the Asgard location. Everyone does their job and the gate starts dialing, Carter is able to get through the gate. Apophis sees Teal'c's betrayal and imprisons him, Daniel, Jack and Kawalsky are caught too. Apophis wants to know how is it possible for O'Neill to be alive again and Daniel tries to explain it, but Apophis gets upset.
The Asgard come right at the nick of time and all the Goa'uld vanish. Alternate Carter appears back and alternate Hammond is healed of all injuries sustained during the Goa'uld torture. Everyone is saying good bye and Jack ends up kissing alternate Carter.