Peace returned to the watery planet Latis thanks to crown prince Lord British and the hero of the Gradius Army — but the victory was short-lived. The seemingly defeated Salamander Force has regained its strength and set its sights on Latis once more. Simultaneously, the Gradius Army faces the Bacterian superweapon known as Dark Force. With no hope of aid from their former saviors, Latis's imperial princess takes matters into her own hands, personally piloting the Lord British MK III into battle. She is joined by the Vic Viper Type L, a new vessel built from the combined technologies of both Gradius and Latis.