The planet Gradius, a peaceful Earth-like world, was under attack by their long-time nemesis, beings from the sub-space star cluster known as Bacterion. The people of Gradius, in danger of being completely destroyed by the amoeboid Bacterions, have had to resort to using their secret weapon. To save themselves, the people of Gradius launched the prototype of their new hyper-space fighter, the BP-456X Warp Rattler. The entire galaxy awaited the outcome of the decisive battle between Gradius and the evil Bacterions.