The Sentinel

"The Sentinel" is the twentieth episode of the fifth season of Stargate SG-1.

Synopsis
The Goa'uld System Lord, Svarog, is planning on taking back Latona to his control. The only way to stop him is the Sentinel, a piece of technology capable of defeating him. Unfortunately, rogue NID agents once tampered with the device, and SG-1 gets the ones responsible to make it operational again.

Previously on Stargate SG-1
When a rogue element of the NID led by Colonel Harold Maybourne begins to steal advanced technology from other races, Colonel Jack O'Neill goes undercover and arrests several members.

Plot
The episode begins as Major General George S. Hammond attempts to contact SG-9 on Latona, who are eleven hours late reporting in. SG-9 was attempting to re-establish diplomatic ties with the Latonans, creators of an advanced defensive weapon named the "Sentinel", which was developed over three hundred years ago by their ancestors, to defend the planet. Contact is established with Lieutenant Carl Grogan, a member of SG-9, who reports that SG-9 was attacked by Jaffa and that he is cut off from the Stargate, but is then attacked by a Jaffa patrol and cuts out.

Hammond briefs SG-1, explaining that two years previously an NID team attempted to analyze the Sentinel, to create copies to defend Earth, but were refused access to the weapon by the Latonans. Immediately after the NID team returned from their mission, they were captured, imprisoned, and placed on death row for stealing technology from Earth's allies. Colonel Jack O'Neill volunteers to visit them, as a consensus is reached that the NID team lied and gained access to the Sentinel against the Latonans' wishes and that they somehow damaged the device in the process. O'Neill speaks with Colonel Sean Grieves, who reveals that they disassembled and reassembled the Sentinel in an attempt to understand it. O'Neill asks Grieves to tell him how to fix the Sentinel, but Grieves insists that he and Lt. Kershaw, the other member of the NID team, go with them and have their death sentences commuted to life.

SG-1, SG-3 and the two convicts travel to the planet and find Grogan, the only remaining member of SG-9. SG-9 was attacked by the Goa'uld, indicating the Sentinel is inoperative. Major Samantha Carter, Teal'c, Dr. Daniel Jackson, Grieves and Kershaw trek to the Sentinel to repair it while O'Neill and Grogan set out for the city to offer the Latonans a chance to escape.

Carter's team locate the Sentinel and attempt to disable the force field protecting it, an action which took forty-eight hours the first time, according to Kershaw. Teal'c and Carter fight off a Jaffa patrol while Daniel, Grieves and Kershaw attempt to deactivate the force field. Meanwhile, O'Neill and Grogan attempt to persuade Marul, the leader of the Latonans, to save his people and evacuate the population through the Stargate. Jack is unable to convince him, as Marul insists that as long as the candle in his chambers burns, the Sentinel and its caretaker are protecting them. A Goa'uld Ha'tak begins bombarding the city and Jack tries one last time to convince Marul, but is ambushed by Jaffa and captured.

Daniel succeeds in deactivating the force field as a battalion of Jaffa approach, and it is reactivated in just time to protect the group from the Jaffa, but Kershaw is shot in the back with a staff blast as she activates the force field. Grieves attempts to repair the Sentinel while the Jaffa try to shut down the force field, but he cannot find anything wrong. Daniel then translates a small portion of text on the Sentinel, reading 'Life Force', 'Life Energy', and 'Two as one'. Eventually Grieves admits, at Kershaw's behest, that he shot and killed a Latonan man claiming to be the Caretaker, then Kershaw rigged a dead man's switch that the Caretaker was wearing, so that it was not set off when the Caretaker died.

The Jaffa bring Jack and Grogan to the Sentinel and demand that Carter's team lower the force field. Jack orders Carter to destroy the weapon, but Grieves tells the Jaffa he will deactivate the force field from inside. Jack repeats his order and Carter attempts to communicate to him that she can tell Grieves knows how to fix it. Grieves realizes what they are doing incorrectly, and grabs hold of the Sentinel, making "Two as one". The Sentinel releases a beam of bright light and the Jaffa disappear, as does Grieves; the Sentinel is powered by the life force of a single person, which was the Caretaker's ultimate role. When the beam has passed, Carter realizes Kershaw has died from her staff wounds. Teal'c suggests they ask the Latonans for permission to study the Sentinel further, but Jack merely replies that he believes he already knows their answer.

Notable Quotes
O'Neill: The rat bastard.

Jackson: I thought he came across as very nice.

O'Neill: The voice behind the camera.

Carter: Well, according to his report, the Latonans never granted Greaves' team access to the sentinel device... before they were recalled and arrested.

Jackson: You don't think it's possible for an NID operative to lie?

Teal'c: I believe it is, Daniel Jackson.

Jackson: Right...

Greaves: I'll say this again. I don't like the thought of going into this unarmed.

O'Neill: And.. I don't care.

Kershaw: I feel better just knowing there's an archaeologist watching our backs.

Jackson: Yeah, which end do the bullets go in again?

Grieves: I'll be happy to show you.

O'Neill: Our mission objective is to fix whatever you screwed up. If you get any ideas other than that, I'll shoot you. Understood?

Jackson: Just out of curiosity, how many years did you promise to take off their sentence if they managed to fix this?

O'Neill: Actually they'll get a few more years out of this.

Jackson: More?

O'Neill: They were on Death Row.

Carter: So how did you manage to find the Sentinel if the Latonans didn't want to show it to you?

Kershaw: Maybe we're good?

O'Neill: Bribed the locals, eh?

Greaves: I see you've done your homework.

Teal'c: The Sentinel was indeed a device with great power. It would be wise to ask the Latonans to study it further.

O'Neill: Oh I think I know what they'd say.

Goofs

 * When Major General George S. Hammond attempts to contact SG-9 on Latona, Lt. Carl Grogan responds "General, sir, this is Sergeant Grogan..." despite his being established as a lieutenant in "Proving Ground". Once SG-1 makes contact with Grogan on Latona, O'Neill calls him "lieutenant."
 * When the teams prepare to go through the Stargate to Latona, Colonel Jack O'Neill refers to Major Carl Warren as Major Lawrence. This is possibly a mistake by Richard Dean Anderson as the actor who plays Warren is named Colin Lawrence.

In other languages

 * French: Sentinelle (Sentinel)
 * Italian: La Sentinella (The Sentinel)
 * Spanish: La Centinela (The Sentinel)
 * Czech: Strážce