After Mega Man's previous quest saw the introduction of Bass & Treble, Dr. Wily's new robotic rivals of Mega Man, the threat of Wily's world domination plans intensified. Dr. Wily escaped during his previous battle against Mega Man and has begun to build up his army again. Designing and constructing a new secret castle hidden under the depths of a volcano, Wily began to formulate new plans for the destruction of Mega Man. While out on patrol for Mega Man, Bass finds him and a battle ensues. As always, Bass' overconfidence allows Mega Man to overcome him, but little did either of them know that an event was occurring in outer space that would prove to be very dangerous for both of them. Far off in space away from Earth, two mysterious robots were also locked in battle, with one of the combatants losing fast. The failing robot, the one bent on destruction and hatred, begins a descent into Earth's atmosphere. The other robot races after it, but is too late to stop the evil robot from breaking up and sending it's remains down to the surface. The resulting crash alerts both Dr. Light and Dr. Wily, but Wily manages to find the crash site before Mega Man can. Racing to the scene, Mega Man finds Dr. Wily fleeing with a piece from the crash site, a small meteor which he claims can give him the power to take over the world. Escaping in a small capsule, Wily leaves Mega Man alone at the crash site, but Mega Man discovers the damaged body of the other robot in the remains, and quickly takes it back to Dr. Light for repairs. The alien robot intrigues Dr. Light, and while he conducts repairs on it's damaged body, Mega Man heads out to stop Wily and his eight new Robot Masters.