Basically, the plot is that a space ship travelling runs into some problems, and ends up making a crash landing on an unknown planet. Once they get there, they discover that everything isn't nice and happy, and the interesting group there has to try to find a way home.
I know, put this way, it sounds rather typical and boring. however, it's anything but. The 'fun' stuff they find on the planet (I'll let you watch it to find out what. ;-) as well as the fact that their group is made of up diverse and not always 'friendly' people causes a lot of excitement.
So, if you wanna see a nifty Sci-Fi thriller type movie, Pitch Black would be a good choice. ;-)
I also rented Frequency, and I plan to watch that tomorrow. ;-)