Memento

Memento is the twentieth episode of the sixth season of Stargate SG-1.

Plot
The Prometheus, in orbit above Earth, detects a Goa'uld Ha'tak and prepares to attack, however, it is only a drill. Col. O'Neill, who, together with SG-1 is on the ship, assisting with damage control, isn't happy about the repetitive drills and talks with General Hammond about it. Afterward, the Prometheus starts for their real mission and enters hyperspace.

During the flight, O'Neill talks with Col. Ronson, commander of the ship, about the constant exercises when suddenly, the ship leaves hyperspace. After some investigation, they find out that the reactor’s buffer overloaded because they came in contact with a gravitational wave from a star. In addition, they are unable to repair the buffer and thus decide to fly to a nearby planet (by using the hyperspace engines for only a short jump) where a Stargate was once present. However, after the short flight, the naquadria reactor overloads, forcing the crew to jettison the reactor. It detonates in a massive explosion, discharging an EMP-wave that damages the ship, even with shields. After surmising the damage, they detect long-range ballistic weapons, which originate from the nearby planet. They conclude the hyperspace engine explosion could have been construed as an attack against the planet. Because they have no other options, Col. O'Neill contacts the planet, pleading for them to disengage the rockets which finally explode. Afterwards, they are contacted and given landing coordinates on the world named Tagrean.

The Prometheus lands and SG-1 leaves the ship. Upon going outside, they are confronted with a large army, forced to disarm and brought into a city, where they meet chairman Ashwan and his council. They tell him about the Stargate but it turns out that the council believes it's a myth. After SG-1 leaves, the chairman talks with a commander named Kalfas, who is skeptical of SG-1’s account. Back on the ship, the team looks over several historical documents, given them by the council but find nothing regarding the Stargate. Teal'c and Jonas Quinn then get access to the archive of the Tagreans (after inviting them to a dinner, much to Col. Ronson's protest) but again turn up empty-handed. However, they notice a strange man (named Tarek Solomon) who has watched and followed the two. He clandestinely tells them that he can help. On the ship, O'Neill and Major Carter lead Ashwan and Kalfas on a tour. During dinner, it is revealed that the recorded history of the Tagreans only goes back 300 years because before this time there was a dark age which the humans on the planet want to forget.

In Tarek's office, he shows his visitors relics from ancient times and believes their creator and god to be Heru'ur. Thanks to an old document, they also find out where the Stargate may lay. Jonas and Teal'c are then taken to the place in a desert by Tarek (although Kalfas has an argument with Ashwan about this), where they uncover the Stargate. After unearthing the device, however, they are attacked by Kalfas, who takes them prisoners. When Kalfas ignores Ashwan's orders to release them, Ashwan convinces the soldiers manning the batteries surrounding Prometheus to stand down, allowing it to launch and fly to the location where Kalfas is holding Jonas and Teal'c. Thanks to the help and courage of Ashwan, who convinces  Kalfas’ soldiers to stand down, Kalfas is arrested.

SG-1 uses the Stargate to bring back equipment from Earth to repair the Prometheus. Jonas says goodbye to Tarek and SG-1 heads home.