In the future, humanity has been beset by a horde of alien invaders. Kiva, a human soldier, has captured an alien mecha, the Megas, and remodeled it, planning to send it back in time three years to a pivotal battle so that the humans can win the war. Her plan goes awry when the Megas is fired upon in transit, rocketing it at random through time. She pursues it, as does the alie...