August is over, and that means season 1 is done too. This finale episode is the first of a two-part story, which is concluded in the premiere episode of season 2 (The Serpent's Lair). Because Showtime ordered two seasons of SG-1 right off the bat (does stuff like that ever happen any more?), it gave the writers the opportunity to make a real cliffhanger knowing it'd be resolved, bringing back lots of viewers the next year.
The story does serve as a kind of full-circle for the season by bringing back Alexis Cruz as Klorel-in-Skaara. If you recall, Skaara is an Abydonian who was kidnapped by Apophis in the pilot episode, Children of the Gods, along with his sister, Daniel's wife Sha're. Both were taken as goa'uld hosts, and this is the first time we see either of them return. It's a nice reveal, Apophis introducing his 'son', who then arises from the sarcophagus, and turns to the camera to show his face. He's later killed by O'Neill to save Daniel's life, but of course there's a sarcophagus on board so this is no biggie. They don't even make that big a deal of it, cutting quickly from the grieving Jack to showing Earth out of the window (Interesting sidenote: Today the NASA probe Juno, headed for Jupiter, sent back a photograph of the Earth-Moon system from about 9.5 million kilometres - isn't she pretty?).
The ship arriving at Earth heralds the destruction that Daniel saw in the alternate timeline, but with the Stargate Programme being shut down, and only SG-1 to try and stop it, will the same fate befall our Earth? You'll have to continue watching to find out!