Setting is a planet filled with lush forests.
You have three race choices, terran, protoss and zerg.
Terran : You are a part of the dominion military personal, you must either destroy the zerg spawning grounds or evacuate the civillians, your higher ups have currently given you the order to hold all borders while they prepare evacuations- if the strike team is unable to kill the spawning grounds in time.
Protoss: You are protoss sent to purify the planet. However, your commander was in a slight debt to one of the terran generals for saving him a while back. Instead of purifying the planet, you have set up a base in attempt to aid the terrans in destroying the zerg spawning grounds. However, the general who had been so freindly to the protoss is off-planet and the dominion are getting on all of your nerves. Try to maintain an alliance with the terrans and destroy the spawning grounds before a new batch of zerg hatches.