Starscream, believing Megatron destroyed, forces Doctor Arkeville to take him to his secret laboratory. Once there he discovers another of the Doctor's inventions, the Exponential Generator, a power source that, if it overcharges, will detonate with enough energy to destroy the Earth. Meanwhile on Earth, Megatron has returned to the Decepticons having survived the explosion of his starship. When he learns that Starscream and Doctor Arkeville are apparently working together he sets off in pursuit with the other Decepticons.