Past and Present

"Past and Present" is the eleventh episode of the third season of Stargate SG-1.

Synopsis
SG-1 arrive on Vyus and finds the inhabitants have all lost their memories. The team soon discovers that the culprit is someone they had dealings with before.

Plot
SG-1 arrives through a Stargate in an alien storage facility. They are met by two locals, a man, Orner, and a woman, Mayris, who are amazed that SG-1 has memories which extend back to "before the Vorlix." It seems the entire population of the planet is suffering from some form of amnesia and have no recollection prior to a date "at least a year ago." Additionally, there are no children or "elders" although they have pictures of the "elders."

Orner takes SG-1 to meet an important member of the "Transitional Government" named Ke'ra, who shows them the main library and explains that their society is unstable and badly compromised because of the Vorlix. When Ke'ra discovers they have traveled via the Stargate she produces a notebook made by a scientist before the Vorlix which mentions a "visitor" who came to the planet by the same means. The visitor was "something of an apothecary" and was called "Linea" (see "Prisoners"). SG-1 suspects that Linea, nicknamed "the Destroyer of Worlds", caused the Vorlix, and that they bear some responsibility.

Ke'ra, Orner, and Mayris return to Stargate Command so that Dr. Janet Fraiser can study the problem. She determines that the catastrophic event was related to an insecticide called "Dargol," which had built up in the planet's food chain and prevented conception in the human population, which explains the lack of children. Linea had discovered a derivative of Dargol that had the potential to prevent aging, and/or restore youth--the elders are not missing because the young people left, they are the elders. Amnesia was an unintended side effect.

Their suspicions aroused, the SGC runs a DNA test on Ke'ra, comparing it with DNA taken from Linea. The two samples match, confirming they are the same person. However, Dr. Frasier is unable to synthesize an antidote without Ke'ra's expertise. Reasoning that Ke'ra without her memories isn't really the same person as Linea, Major General George S. Hammond allows Ke'ra to continue assisting Frasier.

Having suspected her true identity, Ke'ra steals a small amount of the antidote and regains her memories. Horrified by the memories and heartless personality she has thus released, Ke'ra attempts to commit suicide. Dr. Daniel Jackson, who has been steadily falling in love with Ke'ra, finds her and stops her in time, suggesting a different way to destroy Linea. Ke'ra takes another dose of the Dargol derivative, causing her to lose her memories again. The Vyans agree to offer the new Ke'ra a home on their planet, and a new life.

Notable Quotes
Upon arriving at the alien storage facility

O'Neill: Anybody gets the feeling these folks don't do a lot of traveling?

Goofs

 * At the beginning of the episode we see and hear the Stargate dialing, but the chevron ring does not move.

In other languages

 * French: Le Passé Oublié (The Forgotten Past)
 * Italian: Passato e Presente (Past and Present)
 * Spanish: Pasado y Presente (Past and Present)
 * Czech: Minulost a přítomnost