An elite military unit (SG-1) must flee back to Earth when two members of their team inexplicably disappear into thin air. But they return to a world in which the Stargate -- an Ancient device which allows them to travel to hundreds of planets -- was never discovered, and their own history has been erased. Now they must convince a dubious government and military that the timeline was altered by a powerful Alien enemy (Ba'al) in order to conquer Earth, and time is not on their side.
Not the best of the Stargate TV universe but definitely not the worst. It's a nice way to tie up any final loose ends left by the Season 10 finale. I'd highly recommend watching this only if you're a fan of SG-1. If not, you'd be fine avoiding this movie.
I'm a HUGE Stargate fan. I just wish they made more movies. This one was good. Ba'al is a tricky bastard and smarter than the average bad guy in the show.