Foothold

Foothold is the fourteenth episode of the third season of Stargate SG-1.

Plot
SG-1 returns from a mission and notices increased security at the base, but are told it is just a precaution due to a chemical tetrachloroethylene spill on Level 23. However, once in the infirmary, the team is promptly sedated.

Teal'c awakens some time later and sees Dr. Fraiser and Hammond speak with unfamiliar aliens about an invasion of Earth. He feigns unconsciousness, then overpowers Siler and frees Carter. Their escape is detected and Teal'c is captured, but Carter escapes Cheyenne Mountain.

Carter contacts Colonel Maybourne about a potential foothold situation and they agree to meet in public. However, when she meets him face-to-face, O'Neill and Daniel are present. Carter is informed that she is suffering from effects of the tetrachloroethylene which can cause paranoid delusions. She reluctantly agrees to return to the SGC.

On the plane ride back to the SGC, Carter notices O'Neill's image flickering. She seizes Maybourne's gun and kills O'Neill and Maj. Davis, revealing their actual alien forms. Maybourne restrains and interrogates "Daniel". Carter finds a small disc (later called a mimic device) attached to the alien's chest and places it on herself, taking on Daniel's image. Another device links the alien to the original person's thoughts.

In the meantime, the real Jack O'Neill and Maj. Davis wake up, hanging from an SGC ceiling in restraints. Other SGC personnel are suspended alongside them, unconscious. They observe the fake Fraiser scanning an SGC member through a device and imparting his appearance to an alien. O'Neill and Davis free themselves.

Carter infiltrates the facility disguised as Daniel and finds O'Neill and Davis. She informs them that Maybourne's NID forces are preparing to storm the facility, so they must find a way to disrupt the aliens' disguise. Carter suggests that the incident on the aircraft may have caused by a certain frequency generated by the engines. Carter duplicates the sound and broadcasts it throughout the base, unmasking the aliens. As Maybourne's forces secure Cheyenne Mountain, the aliens flee through the Stargate. Many of them escape, but Carter shuts down the gate. Trapped, the remaining aliens use a self-destruct.

Notable Quotes

 * Carter: Maybourne, you are an idiot every day of the week. Why couldn't you have just taken one day off?


 * O'Neill: Maybourne? How did he...?
 * Carter: I called him, sir?
 * O'Neill: Willingly?


 * O'Neill: Coat of paint...a little touch up...it'll be fine.


 * Maybourne: Credit Major Carter, I do.

Background Notes

 * An alien foothold of the SGC is a key part of "Proving Ground", and the mimic devices appear again in "Smoke and Mirrors".
 * Continuing storyline: In the beginning of the episode, SG-1 discusses the Harcesis child, a key component of the season three episodes "Forever in a Day", "The Devil You Know" and "Maternal Instinct".
 * Carter leaves Cheyenne Mountain through what appears to be the same shaft that Colonel Cromwell used to gain entry in "A Matter of Time". She justifies the low security at this shaft to the viewer as "The base was designed to keep people out, not in", and the Mountain was experiencing time dilation in the other episode.
 * The unnamed aliens came from P3X-118. They impersonated SG-6 needing medical attention.