Stargate SG-1 : season 5 episodes

(spoilers)

5.01. Enemies
The team discover Apophis' ship taken over by the replicators. They are trapped on another ship, with Apophis and replicators, who speed it back to their own galaxy. They destroy the ship and escape, but Teal'c has been brainwashed by Apophis.
5.02. Threshold
Teal'c undergoes an extreme ritual designed to deprogram him, if it doesn't kill him first.
5.03. Ascension
Carter is found unconscious during a mission. Exhaustion is diagnosed, but during her consequent leave, she is visited by an alien, Orlin, who only she can detect. Orlin convinces her the experiments on the planet she has returned from must cease, but she now needs to convince Hammond she is not delusional. [Eventually, we discover you can construct a one-shot stargate from the things you can buy online.]
5.04. The Fifth Man
O'Neill remains behind to help the fifth team member, Tyler, injured in a Goa'uld attack, while the rest return home for backup. But Hammond informs them there is no fifth member, and locks down the stargate while the puzzle is investigated. [Oh, glorious triumph of rationality -- the team eventually decide, based on the evidence, that there is indeed no fifth team member!]
5.05. Red Sky
SGC have overridden some security protocols, allowing the wormhole to pass through a planet's sun, damaging it. All the people will die if the damage is not reversed, unless they can be persuaded to evacuate. But they are sure that Freja, their Asgard god, will save them in time, and stay put. O'Neill contacts the Asgard for help, but they inform him they cannot, as that would violate their treaty with the Goa'uld, and put all the galaxy in danger. So Carter must come up with a miracle to save the sun. She fails, but the effort is good enough to allow the Asgard to help covertly.
5.06. Rite of Passage
Cassandra [ 1.15. Singularity ] starts undergoing a dangerous change. SG-1 discover that it is part of an experiment Nirrti was doing on her people. They capture Nirrti, and force her to save Cassandra.
5.07. Beast of Burden
The Unas that Daniel befriended [ 4.08. The First Ones ] has been captured by slavers. Daniel insists they rescue him, and ends up witnessing the start of a slave revolt.
5.08. The Tomb
SG-1 and a Russian team investigate a planet where a previous Russian team disappeared. The Russians are acting under additional secret orders to recover a powerful artifact. But an accident leaves them all entombed, with a Goa'uld symbiont on the loose.
5.09. Between Two Fires
The Tollan [ 3.15. Pretense ] have seemingly reversed their policy on giving technology to Earth, and are offering an ion cannon. O'Neil and the team are suspicious of this change of heart, and receive a warning of danger, so they ask for 38 ion cannons, enough for full planetary defence. The Tollan agree. SG-1 discover the cannon are useless against new Goa'uld shields, and the Tollan High Council is acting under Goa'uld control, building a super weapon. Then the Goa'uld order the Tollan to use the new weapon on Earth.
5.10. 2001
SG-1 discover a race who have friends who offer them help against the Goa'uld. But Daniel discovers worrying evidence of population decline on the local planet. These friends turn out to be the same aliens that nearly destroyed the future Earth [ 4.16. 2010 ] , before having their coordinates removed from the SGC computer. Despite warnings from the team, Earth politicians want to go ahead. The race is on for Sam and the Ambassador (who was her husband in the other future Earth) to get proof before it's too late.
5.11. Desperate Measures
A dying billionaire snatches a Russian Jaffa prisoner, and Major Carter, desperate to find a cure. O'Neill enlists disgraced Colonel Maybourne's help to find Carter. The patient is fading fast, and his doctors implant the symbiont too soon, desperate to cure him. They plan to dissect Carter's brain to find out how she survived, but O'Neill finds her first. Of course, the symbiont takes over, so there is now a Goa'uld on Earth, eventually captured by Colonel Simmons [John de Lancie].
5.12. Wormhole X-Treme!
Marty the stranded alien [ 4.11. Point of No Return ] is now Consultant on the TV show Wormhole X-treme! , with a plotline that bears a strange resemblance to a certain Stargate team. He's suffering amnesia, but his alien friends are back, after the ship approaching Earth. [The 100th episode, played for meta-laughs.]
5.13. Proving Ground
O'Neill is training some new SG recruits (including Carter's cadet [ 4.19. Prodigy ] ) when there's an emergency, leaving the untried team to save the Stargate.
5.14. 48 Hours
A Stargate is destroyed as Teal'c is in the wormhole, leaving him stranded in a temporary buffer. The gate must be shut down, or he will be erased. Sam works desperately to get him back, while pressure comes from on-high to restart missions. Maybourne tells O'Neill that Simmons has the billionaire Goa'uld [ 5.11. Desperate Measures ] , so he goes to him to find a solution. The Russians reluctantly lend their dialling device to help.
5.15. Summit , part I
The Tok'ra have invented a Goa'uld poison. Daniel Jackson infiltrates a Goa'uld summit, to poison all the System Lords in one fell swoop. But an envoy arrives -- it's Daniel's Goa'uld infested ex-girlfriend [ 4.13. The Curse ] . She represents a new powerful System Lord, Anubis, and Daniel realises the poison plan would merely create a power vacuum for him to step into.
5.16. Last Stand , part II
The Goa'uld are attacking the Tok'ra base to get the secret poison, and Carter, O'Neill and Teal'c are trapped in the crystalline underground. Jackson escapes in a flier from the unpoisoned System Lords summit to rescue them, crashing the flier on arrival.
5.17. Failsafe
An asteroid is about to obliterate Earth. The Asgard won't help, because their treaty with the Goa'uld excludes natural disasters [ 5.05. Red Sky ] . SG-1 repair the crashed flier [ 5.16. Last Stand ] , and attempt to blow up the asteroid. But they crash, because the rock is made of Naquada -- it is a Goa'uld device. At the last minute, the team manage to use the hyperdrive to make the rock pass through the Earth.
5.18. The Warrior
Kytano, First Prime of Imhotep , has killed him as a false god, and is building up an army of free Jaffa, leading many successful raids against the Goa'uld. SG-1 go to offer an alliance with Earth, but O'Neill is worried by the new leader's readiness to sacrifice his men's lives. Teal'c joins in a mission, only to discover they have been betrayed. Kytano is really Imhotep, and the System Lords have been using him to flush out false Jaffa.
5.19. Menace
SG-1 find an android alone on a devastated planet. They take her back to base, and revive her. Initially she seems friendly and childlike, but her replicator toys [ 3.22. Nemesis ] have everyone worried...
5.20. The Sentinel
The illegal NID team [ 3.18. Shades of Grey ] appear to have broken the Sentinel, a planetary defence system. A Goa'uld mothership is on its way to take the planet, and SG-1 need the help of the original team to repair it.
5.21. Meridian
Daniel returns from a mission with a lethal dose of radiation, being accused by the alien government of sabotage. The rest of the team set out to clear his name, and save his life. O'Neill shames one of their scientists, Jonas Quinn, into admitting Daniel actually saved millions of lives by stopping an explosion. Daniel decides to ascend to a higher plane as a twisty light being [ 3.20. Maternal Instinct ] , rather than be cured by Jacob Carter.
5.22. Revelations
The team is mourning Daniel's loss when Freja comes through the wormhole: a powerful new Goa'uld ship has killed Thor, and is attacking a vital Asgard research laboratory, and the Asgard need SG-1's help. They go, only to discover Thor not dead, but a captive of the Goa'ulds, being tortured by Anubis [ 5.15. Summit ] for his knowledge, and that the Asgard are a dying race of clones, with this laboratory their last hope to save their kind. Lots of to-ing and fro-ing, but eventually they all escape, with Thor in a coma from a novel piece of mind downloading technology. The Asgard have found out from the recently discovered android [ 5.19. Menace ] how to defeat the replicators, but Anubis appears to have found new technology even more powerful than the Asgard's.