Stargate SG-1 - Season 3 Episode 6 -

The quantum mirror Daniel found in "There But for the Grace of God" brings to Area 51 an alternate Kawalsky and Dr. Carter from another reality, this time one where Sam never joined the military but became Jack's wife and the Goa'uld just overran earth. Dr. Carter begins suffering from temporal entropic cascade failure, a paradoxical effect of having two versions of the same person in the same reality and realises that she must return to her own reality or both Sams will eventually perish. SG-1 embark to the alternate reality to intercede and prevent the Goa'uld from ...