Stargate SG-1 picks up where the blockbuster film left off. Col. Jack O'Neill (Richard Dean Anderson) and his SG-1 team: Daniel Jackson (Michael Shanks), Teal'c (Christopher Judge), and Capt. Samantha Carter (Amanda Tapping) set out to explore the mysteries of the Stargate. Each mission through the gate takes the team to new worlds in a seemingly boundless universe.
SG-1 returns to Stargate Command with news that Earth has been saved from the Replicators — only to learn that one of the deadly creatures was not destroyed.
After crashing into the ocean aboard the ship of Asgard leader Thor, the Replicator bug found its way into a Russian submarine, where it killed the entire crew and continued to rapidly replicate.
Col. Jack O'Neill suggests the sub be towed out to sea and nuked, but the Pentagon feels that such an act could cause a serious situation with the Russian government. Instead, O'Neill and Teal'c lead a small, heavily armed team aboard the sub in the hope that the Replicators can be eliminated by sheer firepower.
Maj. Samantha Carter is taken to the Asgard's home planet, Cimmeria, which is on the verge of total destruction by the Replicators. Thor believes that Carter's human knowledge might hold the key that will enable the Asgard to defeat the Replicators once and for all.
Stargate Command is contacted by Alar, a representative of the planet Euronda. His people are under attack and in need of help. Gen. Hammond sends SG-1 on a humanitarian mission to deliver food and medical supplies.
The team arrives to find a civilization devastated by war — and a leader desperate to make a deal. In exchange for the heavy water Euronda needs to sustain its defensive fields, Alar is prepared to offer advanced Eurondan technology to Earth.
Col. Jack O'Neill quickly agrees to the trade. Dr. Daniel Jackson, however, is suspicious that the Eurondans have not been completely honest about their agenda, and he sets out to discover their true motives.
Anise, a new Tok'ra representative to Earth, approaches Stargate Command for help in testing some mysterious armband devices discovered amid the ruins of a distant planet. Anise believes the devices could be a powerful weapon in their war against the Goa'uld.
Because symbiotes seem to render the devices ineffective, she requires human test subjects to prove her theory. Col. Jack O'Neill, Maj. Samantha Carter and Dr. Daniel Jackson volunteer. They are outfitted with armbands and, within a short time, begin to demonstrate incredible strength and speed.
Dr. Fraiser becomes concerned, however, when medical tests suggest that the devices might be endangering their lives. Gen. Hammond orders the armbands removed — only to discover that the devices will not come off.
Anise sees an opportunity and suggests that SG-1, now outfitted with the armbands, be sent to destroy a new ship being built by system lord Apophis. The general flatly refuses and orders SG-1 to remain on the base.
Unfortunately, Anise isn't taking no for an answer. SG-1, its judgment clouded by the alien devices' influence, defies Hammond's order and sets off on what could be a suicide mission.
SG-1 responds to an incoming wormhole with their ally Bra'tac's signal. Instead of Bra'tac, they greet Shan'auc, who tells them that she has come on behalf of Bra'tac.
Teal'c goes to Shan'auc and it is immediately evident to all that the two share chemistry and history. Shan'auc claims to have discovered a way to communicate with her symbiote, and it, in turn, has shared memories with her. These memories, she believes, could be the means to defeat the Goa'uld.
Shan'auc claims that through their communications, she has convinced her symbiote that the Goa'uld are evil. The symbiote is prepared to tell all it knows to the Tok'ra. Teal'c is skeptical of Shan'auc's claim — until he, himself, shares a memory with his symbiote.
The Tok'ra agree that Shan'auc's symbiote is of great value, and they find a willing host for it. Will the symbiote continue to tell its secrets and offer a method to defeat the Goa'uld — or has it cleverly deceived Shan'auc, SG-1 and the Tok'ra into letting it inside their defenses?
During a meeting with the Tok'ra high council, Maj. Graham of Stargate Command goes berserk, firing uncontrollably upon the Tok'ra before taking his own life.
SG-1 is stunned to discover that Graham was a Zatarc, the victim of Goa'uld mind-control technology. According to Anise, its victims are subconsciously programmed to kill, their recollection of the procedure covered by false memories. Anyone who has come into contact with the Goa'uld could well be a Zatarc — and wholly unaware of the fact.
Through the use of an experimental testing device designed by the Tok'ra, Anise sets out to determine who at Stargate Command might have been programmed. The test proves successful in uncovering a second Zatarc — Lt. Astor, a former teammate of Graham's, who also goes berserk, shooting up Stargate Command before turning her weapon on herself.
Subsequent testing then uncovers false memories in two more members of the Stargate program: Col. Jack O'Neill and Maj. Samantha Carter.
While exploring planet P4X-639, the SG-1 team meets Malikai, a human explorer from another world who shares Dr. Daniel Jackson's interest in an alien computer covered in a strange Latin-like script.
As solar flares flash from the red sun overhead, Malikai warns Daniel that the geomagnetic disturbance may be dangerous to the SG-1 team and tells him to leave. When Daniel ignores him, Malikai zaps him with a weapon and begins to program the alien computer.
Maj. Samantha Carter and Teal'c rush to Daniel's aid and are caught, with Malikai, in a mysterious blue light. Suddenly, they find themselves back at Stargate Command, ten hours earlier, preparing to head off on the mission from which they've just returned.
And then it happens again. And again. And again.
As Col. Jack O'Neill returns to eat the same plate of Froot Loops over and over again, he realizes that SG-1 is caught in a time loop and that only he and Teal'c retain their memories through each ten-hour cycle. It's up to them to decode the message on the mysterious machine and figure out a way to break the loop.
When the stargate won't open, trapping teams offworld, the SG-1 team investigates and learns that the Russians have their own stargate, apparently recovered from the sea after an Asgard ship crashed on Earth.
The Russian stargate is locked open, maintaining a perpetual wormhole that defies explanation. At the request of Russian scientist Dr. Svetlana Markov, the SG-1 team is dispatched to the Russian stargate facility, where they make a shocking discovery: All the soldiers and scientists are dead and the stargate remains locked open, connected to a water-covered planet.
Svetlana explains that the Russians had retrieved a sample of the water and found it has amazing properties, including the ability to emit significant levels of energy. That same water, however, seems to have disabled the drone, leaving it inoperable and sending transmissions that are keeping the stargate open.
Dr. Daniel Jackson, Maj. Samantha Carter and Dr. Markov travel through the wormhole in a miniature submarine, in an attempt to recover the drone. The water brings the sub to a halt and begins to crush it, leaving the team unable to return through the stargate.
Back at the Russian facility, Col. Jack O'Neill and Teal'c make their own shocking discovery: Inside a freezer is the frozen body of Col. Harry Maybourne, an SG-1 turncoat who apparently has been advising the Russians. As Maybourne begins to thaw, he comes back to life, spewing out gallons of water and a terrified warning. This may look like water, he says, but it's alive — and it's playing for keeps.
While conducting an archeological dig on planet P3X-888, Dr. Daniel Jackson makes a remarkable discovery: a primordial Goa'uld symbiote, an ancient, predatory version of SG-1's parasitical enemies.
Before he can bring back his sample however, his team is attacked by an Unas. One team member is killed, and Daniel is dragged off into the wilderness by the giant primitive creature.
Learning of Daniel's disappearance, Col. Jack O'Neill leads a rescue mission to the planet. Upon his arrival, he discovers that SG-11 has been almost wiped out — only Hawkins survived — and the planet's water supply is teeming with Goa'uld symbiotes.
While O'Neill and Teal'c struggle with the possibility that one of their men might have been inhabited by a Goa'uld, Daniel is dragged further into the wilderness by his captor. Gradually, he begins to understand a few words of the creature's language.
The Unas, a juvenile whose name seems to be Chaka, saves Daniel's life when he's attacked by a symbiote. As the rescue team struggles to catch up, however, the question remains: Has Daniel become the Unas' newest friend? Or is he simply being brought home as dinner?
Thanks to SG-1, a civilization known as the Enkarans have been transplanted from a Goa'uld slave planet to a safer, more hospitable world.
Soon after the Enkarans settle in, however, problems arise. One of their villages is attacked by a mysterious ship that appears to pose a threat even more formidable than that of the Goa'uld.
SG-1 investigates and discovers that the mystery ship has no hostile intent — it is merely terraforming the planet in order to make it habitable for the Gadmeer, a long-dormant alien species.
Lotan, a biomechanical liaison created by the Gadmeer ship, explains that once the terraforming procedure has begun, it cannot be halted. To do so would mean extinction for the Gadmeer. On the other hand, a completion of the terraforming process will mean certain death for the Enkarans.
SG-1 must find a solution to this ethical dilemma, or face the extinction of an entire species.
SG-1 awakens in a mysterious underground complex, with no memory of their previous lives. In fact, they seem to possess a whole new set of memories.
No longer Col. Jack O'Neill, Maj. Samantha Carter, Dr. Daniel Jackson, and Teal'c, they are Jonah, Therra, Carlin and Tor, laborers doomed to a dreary existence, working the mines beneath an ice-covered planet.
Back at Stargate Command, meanwhile, Gen. Hammond faces the possibility that SG-1 has perished on the planet's icy surface, an outcome he refuses to accept.
As the general tries to unravel the team's mysterious disappearance, the members of SG-1 grasp at fleeting memories of their former lives, memories that are not just the keys to their freedom, but to their very survival.
Stargate Command is contacted by a rambling individual who claims to possess full knowledge of a host of government conspiracies, from the Kennedy cover-up to CIA-sanctioned microwave harassment of Libertarian candidates. He sounds like a crackpot, someone hardly worthy of their attention — until he mentions the stargate.
Gen. Hammond wants to play it safe. They need to check this guy out. Col. Jack O'Neill meets with the mystery caller, a nebbishy fellow named Martin Lloyd, who insists he is an alien and in possession of a spaceship (whose location slips his mind at the moment).
O'Neill is ready to dismiss Martin as a harmless nut and head back to Cheyenne Mountain. Then a series of strange occurrences begin to suggest that maybe, just maybe, there could be some truth to Martin's story....
A test of the X-301, an experimental spacecraft adapted from two Goa'uld Death Gliders, goes awry, sending Col. Jack O'Neill and Teal'c hurtling out of Earth's orbit.
As the X-301 streaks through space at a million miles per hour, Stargate Command struggles to find a way to retrieve it. After an attempt to alter the spacecraft's course fails, things look grim.
Dr. Daniel Jackson seeks the help of offworld allies. He learns that the Tok'ra have a ship capable of reaching O'Neill and Teal'c, but it is on a covert mission in Goa'uld-controlled territory.
With time ticking down and the lives of their comrades hanging in the balance, Daniel and Maj. Samantha Carter must locate the Tok'ra ship, intercept the X-301, and pull off a daring rescue.
When Dr. Daniel Jackson's old archeology professor, Dr. Jordan, dies in a mysterious lab explosion, Daniel pays a return visit to his old academic stomping grounds.
As Daniel reacquaints himself with his former colleagues — including his former girlfriend, Sarah Gardner, Jordan's research assistant — he begins to suspect Jordan's death might not have been an accident.
Daniel discovers that one of the items the professor was studying, an ancient Egyptian jar, contains a perfectly preserved Goa'uld symbiote.
Apparently, a crack in the vessel compromised the sedative solution within, killing the creature. But further investigation reveals that a second jar might have existed.
With a Goa'uld apparently stalking the campus and the local community abuzz with talk of an ancient curse, Daniel must unravel the mystery before it's too late.
While visiting Chulak to gather support for a Jaffa rebellion, Teal'c is captured by the Goa'uld. The rest of SG-1, unaware of his fate, are dispatched to thwart a burgeoning alliance between Apophis and Heru'ur. But when they arrive at the neutral location chosen for the meeting - an ancient minefield floating in space - they discover that Heru'ur has brought along a gift to seal the deal: a battered but defiant Teal'c. SG-1 is torn. Do they try to rescue Teal'c? Or, as Jacob Carter argues, does the success of their mission outweigh the life of their friend?
When Gen. Hammond announces he is stepping down as head of Stargate Command, Col. Jack O'Neill suspects that there is more to Hammond's decision than he is letting on.
O'Neill is right; as he discovers, the National Intelligence Department (NID) — the quasi-governmental agency that, among other things, runs the classified Area 51 alien-research facility — was behind the change of command. Fed up with the general's inability to acquire alien technology through whatever means necessary, it pressured him into resigning.
When Hammond's replacement, the hawkish Gen. Bauer, breaks up SG-1 and assigns Maj. Samantha Carter the task of building a planet-killing Naquadah bomb, O'Neill decides to take on the NID.
However, O'Neill's only hope of restoring Stargate Command to its proper condition rests in the hands of a most unlikely ally: the traitorous Col. Maybourne.
It's 2010, and a lot has happened in ten years. The Goa'uld have been defeated, and diseases such as cancer have been wiped out.
Earth's saviors are an alien race known as the Aschen. Their advanced technology has not only ensured the planet's safety, but it has won them the respect and friendship of all humanity.
In spite of vast medical advancements however, Maj. Samantha Carter and her husband, Joe, are unable to conceive a child.
The Aschen doctors insist that Carter is fine, but Dr. Fraiser's tests reveal something very different: The Aschen have been lying all along. Carter's investigation reveals an insidious plot to wipe out the human race through a process of slow attrition.
Dealing with this insidious alien threat seems virtually impossible. The Aschen have become entrenched in Earth society. They hold all the reins of power. Challenging them would mean certain defeat.
Finally, SG-1 comes to realize that there is still hope — ten years in the past.
SG-1 is called to Abydos to investigate a strange phenomenon: a whirling sandstorm that seems to whisper Dr. Daniel Jackson's name. When they confront the twisting tempest, it dissolves to reveal a young boy who introduces himself as Shifu, the Harsesis.
Shifu is brought back to Stargate Command, where he undergoes a series of tests. The tests reveal that Shifu is physically normal, but it is apparent to all that the young boy is wise beyond his years. Possessing the genetic memory of the Goa'uld, he undoubtedly has the potential to become a powerful weapon against the system lords.
Faced with this prospect, the Harsesis child sets out to teach Daniel a lesson — by imbuing him with the sought-after genetic memories and launching him on a spiritual journey.
Ultimately, Daniel must face a difficult challenge. Will he use his newfound knowledge to change the world for the better? Or will he allow this knowledge to change him for the worse?
One member of an SG unit has committed suicide, and three others, including Dr. Daniel Jackson, are near death. Their condition is a mystery, but the answer could well lie in a strange offworld temple.
Col. Jack O'Neill, Maj. Samantha Carter and Teal'c check out the site and discover a room with a mesmerizing light display. They conclude that the temple was, at one point, a Goa'uld pleasure palace.
As their investigation progresses, they come to realize that the temple is directly affecting their brains' physiologies — delivering euphoric highs while they are on its premises, and debilitating lows of withdrawal when they attempt to leave.
Trapped, they must find a way to break this otherworldly addiction. A young man who is seemingly unaffected by the strange environment might hold the key to their salvation.
During a visit to the Air Force Academy, Maj. Samantha Carter makes the acquaintance of Jennifer Hailey, a promising young cadet with a rebellious streak.
Carter sees great potential in her, but Jennifer seems determined to sabotage her future with the Air Force. She is fiercely independent, opinionated and resentful of Carter, to whom she is constantly being compared. On the other hand, she is brilliant, and Carter recognizes that, given time, Jennifer will prove to be a formidable asset to Stargate Command.
Eventually, Carter decides to show Jennifer exactly what she can look forward to if she stays the course — by bringing her through the stargate. They visit an offworld research base, where Col. Jack O'Neill and Teal'c are on security detail, "babysitting" a group of ungrateful scientists.
The seemingly routine excursion takes a deadly turn when the team is attacked by alien life-forms composed of pure energy. Trapped and cut off from the stargate, SG-1 must make a desperate gamble to reach safety.
Stargate Command is infected by an alien probe that uploads its program into the base computers, where it accesses sensitive data on Stargate program and its personnel.
The virus program is detected and apparently deleted from the mainframe. Unknown to all, however, the entity's program has downloaded itself into the MALP (Mobile Analytic Laboratory Probe) room, where it continues to thrive, building itself a new body in order to contain the immense volume of data it has purloined.
When SG-1 discovers the entity, Col. Jack O'Neill wants to destroy it, but Maj. Samantha Carter and Dr. Daniel Jackson feel that they should attempt to communicate with it first. Carter tries — only to be overcome by a blast of energy. She is rushed to safety while O'Neill shuts down the entity, presumably killing it for good this time.
However, the rest of SG-1 soon learns that the entity is far from dead. In fact, it now exists in a new vessel, one capable of storing even greater volumes of data: Carter's body.
With the base under siege and the alien entity poised to overwhelm them all, O'Neill and company are confronted with a dire prospect: In order to save Stargate Command, they might have to sacrifice one of their own.
G-1 returns to Juna, formerly known as PX3-989, a planet they — or rather, robot duplicates of them — helped free from Goa'uld enslavement.
Once, with SG-1's assistance, the people of Juna were able to rebel against the forces of the Goa'uld system lord Heru'ur and win their freedom. But now the natives face the vengeful system lord Cronos.
SG-1 is prepared to lead the planet's inhabitants against him, but the people are not eager to trust SG-1, who had told them that they would be safe from the Goa'uld if they buried their stargate. They did as they were told — and the Goa'uld simply returned in starships.
Col. Jack O'Neill and the real SG-1 team must gain the natives' confidence before they can win the battle against Cronos. Fortunately, most of the SG-1 robots have survived and might be of help on this doubly difficult mission.
SG-1 pays a visit to the Tok'ra homeworld. They arrive at Vorash on Cronos' mothership — one of the spoils they claimed following their recent battle with him.
At a meeting with Vorash's High Council, it is revealed that SG-1 intends to lend the Tok'ra the enormous ship in order to help facilitate the Tok'ra's move to a new planet. Tanith is beside himself. Why wasn't he made aware of this plan? Teal'c informs him that he could not be trusted because he is, after all, a spy for the Goa'uld system lord Apophis. The Tok'ra has known all along. An enraged Tanith is taken away.
The Tok'ra begins to move items up to the mothership. Preparations are underway for the extraction ceremony that will remove Tanith's Goa'uld symbiote. But amid all the activity, Tanith escapes his cell and flees to the planet's desert surface.
A search operation is mounted, but no trace of him is found. Then the Tok'ra receives word: Tanith must have gotten a message out to Apophis, who has assembled his fleet and is headed for Vorash.
Maj. Samantha Carter and Jacob devise a plan that, if successful, could deal Apophis a crippling blow. They will 'gate the Tok'ra to another planet, then load the stargate onto the mothership and leave Vorash. Once in position, they will dial the address of the black-hole planet, and then jettison the gate into the sun. Given proper timing, this will cause the sun to go nova and destroy Apophis' fleet.
Everything goes according to plan. They launch the black-hole stargate toward the sun and prepare to flee. Suddenly, a Goa'uld ship decloaks and fires, crippling them. Their weapons systems are disabled. Their hyperdrive is inoperative, and Apophis is closing rapidly.
More important, the countdown has begun on a blast that will annihilate the entire solar system....