When Goa'uld ships orbit around a planet, Thor comes to try and get them to leave, however, his weapons prove ineffective against the Goa'ulds new sheileds, and is taken captive by the Goa'uld. Meanwhile at the SGC, Jack doesn't want a memorial for Daniel as he doesn't beleive that he is dead. Jack, Sam and Teal'c are all mourning Danile in their own way - Jack's is to carry on as if nothing has happened! So they stay on active duty while they find a replacement for Daniel.

Freya one of the Asgards that they have met before, comes through the gate to ask them for help and to tell them Thor is dead. The planet Thor was protecting has a researcher on it in an underground facility who was doing some very important work, they have no free ships and want SG-1 to go in their cargo ship to rescue the scientist. Freya is also going to look at the android Reese to see if they can get any clues on how to beat the Replicators.

When SG-1 get to the planet they meet Heindall who tells them Thor is alive and on Osiris's ship. They manage to talk to Thor and he tells them that Anubis is coming to torture him for info. Jack and Teal'c go to resuce Thor, meanwhile Sam is trying to help them from beneath the planet while Heindall is preparing to evacuate. He tells them that his work is of vital imortance to the Asgard. It turns out the Asgard only reproduce by cloning and they are getting genetic degredation, and Heindall has discovered one of their original ancestors which can save their race by bringing new cells to the cloning pool.

Anubis arrives and implants Thor with a device which downloads his memory to the computer Jack and Teal'c try to rescue him but end up captured themselves. Thor manages to free them using his link to the ship's computer and Sam is helping from beneath the planet - but Osiris has now located the base and she and Heimdall must leave.