O'Neill, Carter and Jackson are trapped on Hathor's planet. Teal'c and Hammond go to Chulak to forge a rescue plan and recover the team.

Sam's father hopes that SG-1 can help find and neutralize Seth, an Ancient Goa'uld who the Tok'Ra believe may still be hiding on Earth after thousands of years.

The Asgard and three Goa'uld System Lords meet at Stargate Command to negotiate a treaty modification, but subterfuge and treachery threaten not only the success of the negotiations, but Earth itself.

When the SG-1 team discover a sealed chamber of nine dead Goa'uld, Daniel Jackson is exposed to the parasites that killed them and threaten to drive him insane.

While employing the help of a planet's highly intelligent children for a project, the team discovers their horrific imposed fate when they reach a certain age.

Alternate reality versions of Kawalsky and Carter are caught at Area 51 after coming through the quantum mirror.

A bounty hunter, tracking down a Goa'uld, captures SG-1 and informs them that they too have a price on their heads.

SG-1 arrives on a planet where a culturally 'medieval Catholic' community lives in fear of an Unas they believe to be a demon, which regularly collects human sacrifices to Satan - in fact hosts for System Lord Sokar's army. When Simon implores SG-1 to spare his beloved Mary and take him instead, they even nurse her chicken pox. Simon hopes they are sent by God to deliver them from the satanic burden, but the canon who rules the village as 'spiritual' leader is faithful to Sokar and fears his authority, which rests on his right to select the 'damned soul' to be sacrificed, has been challenged, so he declares Teal'c a demon and incarcerates all SG-1. Witch-trial-type ordeals see the Jaffa 'proven' a demon and executed by drowning, and Daniel refuses the canon's warning to leave immediately. When Teal'c's symbiote allows a resurrection even Sam hadn't expected, they are all designated possessed and sacrificed, along with Mary. Simon follows the Unas with a staff weapon to liberate them, but he's not alone.

SG-1 come across another SG team being attacked by Jaffa. They offer to help but are shot by the SG team members. When they awake, they find out that the other SG team are Jaffa, loyal to Apophis, who are planning to infiltrate Earth. Can SG-1 convince them that Apophis is dead before the Jaffa fight to the death?

Responding to a help cry from Kasuf, SG-1 and more USAF wipe out a Goa'uld Jaffa guard to save most of the slaves on Abydonia. When Amaunet turns her hand device on Daniel, he can't bring himself to shoot his beloved wife Sha're, but Teal'c saves him by fatally staff-shooting her, and Abydononian funeral tradition squashes his hope of a sarcophagus resurrection. Crushed by grief, Daniel has apparitions of Sha're and, once released from hospital, resigns from SGC claiming the quest for his wife was his reason to join. Daniel's former research assistant, Dr. Robert Rothman, succeeds him in SG-1; but Jack is sure he'll be back. Sha're (or Amaunet's posthumous manual spell?) keeps appearing to Daniel life-like, telling him to forgive Teal'c and together find their boy who, as Harsisis, has all the Goa'uld knowledge in his genetic memory, which, to the Goa'uld, means he must be killed. Daniel agrees to return, but has a secret agenda, too.

The team discovers an early industrial world suffering from collective amnesia and has no elderly people.

Martouf leads a Tok'ra delegation with crushing news for Carter: her father Jacob/Selmak has been captured by Sokar and imprisoned on Netu, an Egyptian name for hell, on a moon of planet Delmal, where prisoners are sent to suffer eternal torture, and from where no one returns; only Jolinar has ever escaped. SG-1 mounts a rescue operation with Martouf, top-priority being any information Selmak can offer about Sokar's plan to subjugate the other system lords, an unprecedented threat for all humanoids in the galaxy. Teal'c must pilot a Goa'uld ship and keep it in orbit as landing is impossible except by small pod, but first Martouf taps into Jolinar's memory, which is partially blocked by some trauma beyond physical torture. Only when they're down and in the custody of Netu's lord Bynarr, does Sam realize he is the key, in a 'personal' way, but not voluntarily, as she had thought. Sokar learns of their presence from Bynarr and orders the team and craft destroyed, but this also means there must be a way out. Bynarr's prime, Na'onak, has, and is himself, a major surprise.

Now that Apophis has revealed himself, he promises the prisoners to overturn Sokar, which requires extracting an irresistibly valuable secret, to which end he drugs Sam with the truth serum 'blood of Sokar.' Apophis also implants a memory device in, and gives the drug to, Jack to torture him using the persona of his young son that died, and Daniel for the location of his Harsesis son. Martouf's love for Jolinar makes him betray that the Tok'ra are on planet Entac - a convincing lie, so Apophis's plan to earn Sokar's gratitude, and then kill him when rewarded with the lordship of Netu, is on a shaky basis. Teal'c must help the Tok'ra Aldwin prepare a nuclear weapon to explode the whole moon when his ship arrives as their last chance to eliminate Sokar, but he decides to rescue SG-1 instead, by flying in the path of the rings device on Sokar's ship when he arrives.

An alien incursion takes control of the base.

The SG-1 team is requested by the Tollan to participate in a trial concerning Skaara and whether he or the Goa'uld parasite, Klorel, has control of his body.

The SG1 team embark on a trip to visit a planet with an idyllic beach, but as soon as they step through the stargate, they find they are back in the SGC. They thought that they just left, but have been missing for hours. They soon discover that an alien device has been implanted in their brains and a being called Urgo reveals himself to the team. But no one else can see him and he is extremely irritating. Will they be able to extract him before they lose their minds?

After a cataclysmic meteorite bombardment, Col. Jack O'Neill finds himself stranded on a primitive planet with its Stargate apparently permanently inaccessible.

Col. O'Neill is dismissed from the SGC for stealing alien technology, and is subsequently approached to participate in an even more covert Stargate operation.

While redialing old Stargate addresses, the SGC discovers that a gate that was previously buried has become uncovered. They send a probe through and find two archaeologists. However, when they travel through the Stargate, they find that it is located in a society in civil war: one continent believes that the people were created by a Goa'uld, whilst their enemy believes that humans arrived from another planet - by the Stargate. O'Neill, Carter and Jackson are captured by the authorities and questioned, but Teal'c is wounded and blinded. Can he help SG-1 escape the hostiles and get back through the Stargate?

SG-1 believes they have finally found Kheb, a planet with a temple where they believe the child of Apophis and Sha're, a Harcesis with all the knowledge of the Goa'uld, is being held.

The SGC send a MALP to a huge pyramid and inside they discover a crystal skull like the one Jackson's grandfather found many years before. SG1 visit the planet and whilst Daniel is looking into the eyes of the skull, as his grandfather did, an energy field envelops him. Teal'c fires his Zat at the skull, but Daniel has disappeared. Carter collapses and the team minus Daniel return to the SGC. Teal'c returns to collect the crystal skull, but will he be able to find Daniel?

Ready to go on vacation, O'Neill is beamed away by the Asgard. Thor tells him that Earth is faced with an enemy even worse than the Goa'uld.