Teal'c is unhappy with his son's plans to marry. Ishta arrives bringing news that Hak'tyl may be compromised. Complications arise when O'Neill allows Hak'tyl to inhabit SGC until a new homeworld is found for them.

When the Stargate gets beamed out of SGC in the middle of the night, Teal'c is stranded off-world. Dr. Jackson and Colonel Carter attempt to recover the gate.

SG-1 is sent to warn Harry Maybourne that the goa'uld System Lord Ares is coming to the planet where he was banished, and in the process they find what may be an Ancient time machine.

After a long absence, Jacob Carter returns to the SGC to tell Jack that the galaxy is under threat of takeover by the Replicators. The Goa'uld are under attack from the Replicators and are quickly being eliminated. Ba'al's armies are being destroyed and he arrives at SGC to suggest they work together to defeat their common enemy. Carter's doppelganger, RepliCarter, is leading the attack and she has kidnapped Daniel Jackson in the hope of learning of any weapons the Ancients may have created that could defeat them. Jackson gets help from an unexpected source - the Ancient, Oma Desala - or so he thinks.

Daniel finds himself in a strange time and place - a diner where Oma is working as a waitress. She gives him a clear choice - he can choose to die or to ascend but if it's the latter, he will not be able to help his friends fight Anubis, who has yet to be disposed of. He strikes up a conversation with another patron, Jim, who has his own take on the situation. Meanwhile, Sam decides the time has come for her fiancé to meet her father, Jacob. Jacob is not well, however, something he has kept from Sam for several weeks. After Pete surprises her - he thinks he's found the perfect house for them - Sam realizes she has to come to grips with her feelings for someone else. Teal'c and Master Bra'tac have information that Anubis may be gathering what remains of his forces for an attack on Dakara.

SG-1 is tasked to accompany members of the International Oversight Advisory, including Richard Woolsey, on a tour of the Gamma site. The visitors are suitably impressed but everyone is put in danger when a carnivorous insect escapes from the lab. The base is locked down and no one is allowed to travel through the gate. The bug is linked to the Ori - it's appeared on several planets that they've visited - and Daniel thinks it may be their follow-up to the virus. SG-1 and the IOA visitors take refuge in a cave, but Gen. Landrey is left with little choice but to flood the planet with a deadly neurotoxin to destroy the bugs. SG-1 looks for away out before that happens.

The SGC is approached by an Al'kesh bomber which lets itself be taken down, so they can capture Ba'al, who offers to exchange the necessary information to find Merlin's weapon for human help to eliminate his clones, which want to kill him. They mistrust his story, as does NID Agent Malcolm Barrett, who, however, fails to take over the investigation. Since the captive might actually be a clone, several missions to different planets retrieve and capture all clones, but which is the real Ba'al, and what are his true intentions?