The Sentinel is a planetary defense system which requires that its human Caretaker directly interface with it in order for it to be activated. The device removes invaders in flashes of light, presumably killing them. (5.20 "The Sentinel")
Three hundred years ago, the Latonans built the Sentinel, a planetary defense system designed to protect the people while they pursued matters of the mind and spirit. This system had been successful in keeping the Goa'uld from invading these peaceful people's planet and taking them as slaves.
When the rogue NID cells operating under Col. Harry Maybourne learned of this defense system, they went to the planet to gain access to it. The Latonans would not permit them to see the device, but one of Maybourne's teams, under the leadership of Col. Sean Grieves, was able to find it. It took them over 48 hours to penetrate the device's defense shield because the combination to deactivate the force field was randomly generated and based on "the mathematical progression harmonic in each given pattern altered to its spectral equivalent."
After Maybourne and his rogue cells were arrested for treason (3.18 "Shades Of Grey"), the SGC attempted to make amends with the people of Latona and hoped to gain access to the technology. They sent SG-9 to talk with Marul, the Latonan leader. While they were there, the Goa'uld System Lord Svarog attacked and the planet was under siege for three days before the SGC sent in SG-1 and SG-3 to retrieve their people. They figured that the Sentinel was somehow damaged when Grieves' team accessed it, so they took Grieves and Lt. Kershaw with them in order for them to attempt to fix the device.
The rescue party arrived on the planet to find that Lt. Grogan was the only survivor of SG-9. The rest were killed by Jaffa patrols in their attempt to get to the stargate. Jack asked Grogan to take him to Marul in the city so that they could talk about evacuating their people.
The Latonans were no longer aware of how their technology worked. According to Lt. Grogan, they had technologically regressed and were fine as long as everything remained operational, but once something broke down, they were literally clueless.
In Marul's office there was a flame which indicated that the Sentinel was operational. Marul was not aware that when Grieves and his team came to their planet two years ago, they had killed the Caretaker when he discovered them there. There was a deadman switch that the Caretaker wore to indicate if he was still alive—this device controlled the flame in Marul's office. Kershaw modified the switch so that the flame continued to burn, even though the Caretaker was dead.
Daniel was able to predict the random pattern on the force field protecting the Sentinel and Grieves and Kershaw went inside the cave to see what they could do to fix the problem. When Grieves' team was there before, it had taken them two weeks to get in, take the device apart, and put it back together. Kershaw insisted that the device was put together correctly when they left, but Grieves felt that there was something they must have put out of place. When Daniel was able to read some of the symbols written in a language he had encountered on another planet, he helped Grieves and Kershaw put the pieces together on what was wrong with the Sentinel. The symbols Daniel recognized represented "life force" or "life energy" and "two as one." Immediately Kershaw surmised that the Caretaker and the Sentinel had to interface in order for the device to work.
When the Jaffa ground troops found their way to the Sentinel cave, Carter and Teal'c joined Daniel, Grieves, and Kershaw behind the protective force field. Kershaw, however, had been hit by a staff weapon blast just as she was able to activate the force field and she later died from her wounds. When the rest of the Jaffa brought Jack and Grogan to the cave and tortured them in front of their teammates who were on the other side of the force field, Grieves said that he could deactivate the force field from where he was standing, but what he really did was activate the Sentinel by "joining" with it. The Jaffa and Svarog's mothership in orbit were all whisked away to wherever the Latonans' ancestor "divined" three hundred years ago. Grieves disappeared when he activated the Sentinel and is presumed dead.
After these unfortunate events, it is most likely that the SGC was not permitted to return to Latona to learn of the Sentinel's technology. Any information that the SGC might have had access to died with Grieves and Kershaw.
- Col. Jack O'Neill
- Dr. Daniel Jackson
- Maj. Samantha Carter
- Col. Sean Grieves
- Lt. Grogan
- Lt. Kershaw
- Col. Harry Maybourne
--DeeKayP 19:04, 16 Oct 2004 (PDT)