It's the XXV century and human civilization has spread all over eight solar systems; but it's in turmoil. There are constant political and economical tensions, as the eight systems' resources are predated, far from enough to support a race as consuming as ours.
And you just can't go and claim more systems. Mankind is just the youngest race to have been accepted in the Pact of Major Races. Older ones already own any worthy system; it was hard enough to find those eight, and severely terraform planets for almost a century till they were habitable. The observance of said Pact is feeble, and any attempt to colonize an alien system, even if abandoned, could be used as an excuse for war.
And with Earth's totalitarian ways of directing the politics of the seven colonies independentism is growing strong. A tendency fueled by alien races that bear grudges on us, and conspirate to throw us into a devastating civil war.
Yet, despite all the problems, or maybe propitiated by them, there are plenty of opportunities for adventure. Those brave and audacious enough, will make a difference, either for the good of mankind or for their own wealth.