“Descent” is episode three of season six of Stargate SG-1.
Following the events of the previous episode, “Redemption: Part 2”, Jonas Quinn is now part of SG-1, taking the place of Daniel Jackson (who Ascended in “Meridian”, even though most of the SGC think he’s dead).
In “Revelations” the Asgard, Thor, had a device implanted in his brain by Anubis that was designed to download all his knowledge into Anubis’s computer. Although the device was removed, Thor lapsed into a coma.
SG-1 is approaching a Ha’tak that’s orbiting earth in a Tel’tak, one that seems to be the same one that captured Thor, only it is deserted with no lifesigns. They board it, and O’Neill is planning to salvage the ship, but Jacob thinks it’s a trap. Jacob’s right – sort of. The Ha’tak crashes into the ocean, leaving some of SG-1 stranded inside it.
I think they’ve got yet another new credit sequence, one with more action in it than the previous ones – the first was only looking at Tutankamun’s death mask, the other only at the stargate.