Alpha Centauri starts where Civilization II finishes.
When the colony ship from Earth reaches Alpha Centauri, the crew, once a united group, have splintered into seven factions.
You are the leader of one of these factions as you explore this new world and attempt to gain the upper hand against the other groups. Research new technologies, make alliances, and betray your friends, all whilst defending your territory from those annoying aliens that seem to think they have some right to this planet.
Alpha Centauri for Linux comes complete with the Alien Crossfire expansion pack. This expansion sets the scene for the return of a powerful alien race who plan on using your newly colonised planet for their own ends. How do you feel about that? After all your work in making the planet yours, someone comes along and wants it back! Surely you aren't going to let them have it. Are you?