There was a time, thousands of years ago when 'visitors' arrived on earth and chose humans for a great experiment. They gave humans the ability to learn in order to watch them evolve and expand their minds beyond their primitive means.
Now the experiment is complete and the 'visitors' have returned to harvest their crop. At this moment, their great ships are arriving at major cities around the globe preparing to conquer and claim what is rightfully theirs... the human race.

To stop the invasion you must complete 4 separate missions by defeating the invading aliens that are abducting and mutating humans, snatching monuments and creating havoc in the world. The fate of the plant is in your hands!