You whomped the aliens from the Alpha Proximian Empire in classic Defender and sent them home to cry. Now they want the planets that Earth is mining for desperately needed, life-sustaining minerals. Your job is to protect the space miners as they perform their vital work. The aliens will try to capture them and use their life-energy to turn their ships into hyper-fast mutants. Rescure the captives and destroy the aliens or Earth is history!