In the future the world has become nearly uninhabitable. The remaining humans, calling themselves the Tempus, have devised a plan to change the past. By going back in time they suppress mankind of the present through their superior technology and firepower, to stop humanity in its tracks.
You disagree with the methods of the suppressors. Against all odds, you try to reach the Tempus Turris, a time machine the size of a huge sky scraper. By using stolen time travel technology you attempt to stop their plans of messing with time.