In the darkest reaches of infinite space, pure evil lies in wait ... The Dark Forces led by the god of destruction, Bacterian, prepare to launch a massive onslaught against the planet Gradius. Possessing unstoppable power, the Dark Forces threaten to plunge the Universe into total war and complete annihilation.

Their invasion force smashes the Gradius defenses, and the surrounding planets soon fall like dominoes. Now Bacterian's evil grasp reaches for the heart of the resistance...planet Gradius itself...

To counter the oncoming threat the United Gradius World Forces gather all their fighter craft. Half of them form a defensive net - the other half a strike team. But they are badly outnumbered and The Dark Forces easily tear through their thin frontline. No fighters survive the slaughter....

In a last gasp move, the United Gradius World Forces send out two fighters, previously considered too dangerous for combat missions: The InterDimensional VIC VIPER fighters.

The Fighters take off for the heart of darkness to join the fray that will decide the fate of the Universe...