Little does SG-1 know, mysterious aliens have taken control of Stargate Command and are impersonating the personnel. Teal'c and Major Samantha Carter notice and escape. While Teal'c tries to stop them, Carter reluctantly seeks the NID to help stop them.
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. Janet Fraiser and Major General George S. Hammond speak with unfamiliar aliens about an invasion of Earth. He feigns unconsciousness, then overpowers MSgt. Sylvester Siler and frees Major Samantha Carter. Their escape is detected and Teal'c is captured, but Carter escapes Cheyenne Mountain.
Carter contacts Colonel Harold Maybourne about a potential foothold situation and they agree to meet in public. However, when she meets him face-to-face, Colonel Jack O'Neill and Dr. Daniel Jackson 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 Stargate Command.
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 Major Paul Davis, revealing their actual alien forms. Maybourne restrains and interrogates "Daniel". Carter finds a small disc (later called a Mimetic imaging 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 O'Neill and 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.
Amaunet; Foothold situation; Harcesis; Iris; Iris Deactivation Code; Kheb; Level 16; Level 23; Lightning; Mimetic imaging device; Mimetic thought processor; NID; P3X-118; The Pentagon; Planet (Foothold); Scanning device; SG-6; Sha're; Shifu; Stargate Command armory; Stargate Command infirmary; Stargate Command monitoring station; Stragoth; Suicide; Tetrachloroethylene; Washington D.C.; Zat'nik'tel
Jackson: The remnants of a temple we discovered led me to believe we'd found Kheb. The planet Sha're told me about.
Teal'c: However, there was no sign of Amaunet's Harsesis child.
O'Neill: (shouting) Just rain. Much rain. Wind, lightning, hail. Did I mention the rain, sir?
O'Neill: How is a needle in my butt going to get water out of my ears?
Frasier: It isn't. Come on sir, you know this is standard procedure.
O'Neill: We should rethink this procedure.
(During Major Carter and Teal'c's escape attempt)
Teal'c: Our escape has been detected.
Carter: We won't make it out this way now.
Teal'c: You are correct. I will purchase time for you to depart this mountain.
Maybourne: So. You came to the one person you don't trust.
Carter: I don't know how far up the chain of command the infiltration goes. It may well be contained within the SGC, but if General Hammond was compromised...
Maybourne: He sounded fine to me on the phone.
Maybourne: He called me, Major. Calm down. He's concerned for you, that's all.
Carter: I told you we had a foothold situation.
Maybourne: Major, a chemical spill causing paranoid delusion is infinitely more plausible to me than aliens taking over the SGC.
Carter: My God. You don't think I can tell the difference between the two? What was I thinking?
O'Neill: Oh hi, Carter.
Carter: Maybourne, you are an idiot every day of the week. Why couldn't you have just taken one day off?
Carter: (as Jackson) Colonel?
Carter: It's you?
Carter: It's good to see you. Oh my god. I figured they had to be keeping you alive to access your mind—
O'Neill: Woah! Hey. Who are you?
Carter: Sir? Oh! Sorry.
Davis: Major Carter?
O'Neill: Oh. Well in that case, it's good to see you too.
(attempting to rescue Teal'c by pretending to the guards to be an alien)
O'Neill: (monotone voice) I have come for the bald prisoner.
(the guards open the door and Jack steps inside)
O'Neill: (to Teal'c) You will come with me.
Teal'c: I will submit to no further experiments.
O'Neill: Oh, but you will...
O'Neill: Maybourne? How did he...?
Carter: I called him.
Carter: They self-destructed.
Teal'c: Their destruction appears to be complete.
Carter: That's a lot of damage.
O'Neill: Coat of paint...a little touch up...it'll be fine.
Maybourne: Credit Major Carter, I do.
- An alien Foothold situation of Stargate Command is a key part of "Proving Ground", and the Mimetic imaging device appear again in "Smoke and Mirrors".
- 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".
- Major Samantha Carter leaves Cheyenne Mountain through what appears to be the same shaft that Colonel Frank 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 Stragoth came from P3X-118 impersonating SG-6 needing medical attention but during the conversation between the two impersonating Major General George S. Hammond and Dr. Janet Fraiser, Fraiser referred to the Goa'uld as "the dominant parasitical species of this galaxy". This may indicate they came from another galaxy and are searching for a new home. Their infiltration of Stargate Command was an effort to evaluate the planet's potential for livability before an invasion.
- This is the first of sixty-four episodes of Stargate SG-1, Stargate: Atlantis and Stargate Universe directed by Andy Mikita.
- Dion Johnstone (Stragoth 2) previously played Captain Nelson in the Stargate SG-1 episode "Rules of Engagement" and Na'onak in the episodes "Jolinar's Memories" and "The Devil You Know".
- Richard Leacock (Colonel Brogen) previously played Sergeant in the Stargate SG-1 episode "Bane".
- Alex Zahara (Stragoth leader) previously played Xe'ls in the Stargate SG-1 episode "Spirits" and Michael Clark in the episode "1969".
- When Teal'c knocks out MSgt. Sylvester Siler, Siler puts his legs on the stretcher himself.
- When Colonel Jack O'Neill and Major Paul Davis awaken and capture the alien impersonating Dr. Janet Fraiser, they talk of having to tie her up. After Major Samantha Carter's entrance as Dr. Daniel Jackson, they follow her out to get weapons without ever actually dealing with the alien.
- After Fraiser gives Carter the needle and she passes out, you can clearly see the still-full syringe in Fraiser's hand.
- When SG-1 were sedated and taken to level 23 to be "scanned" so that the Stragoth could add their images to the mimic devices, they were all wearing their olive drab pants and black t-shirts, however when the two Stragoth who were impersonating Colonel Jack O'Neill and Dr. Daniel Jackson met Major Samantha Carter and Colonel Harry Maybourne at the outdoor cafe, the mimic device images of O'Neill and Jackson were wearing different clothes than were scanned at the SGC.
In other languagesEditar
- French: Invasion (Invasion)
- Italian: Base d'appoggio (Foothold)
- Spanish: Asentamiento (Settlement)
- Czech: Nouzová situace (Emergency Situation)
- Hungarian: Invázió(Invasion)