Our hero Bob, having just returned from a secret mission to destroy an evil scientist at the center of the Earth, finds he is deep underground. Worse, it seems that although he has defeated the evil scientist, it was not in time to save the planet from the powerful guards and deadly flying robot drones that he unleashed. Bob must make his way from the deep underground fiery cave, through the heavily guarded city, and forest, high in the mountains, where he hopes to live, free from the terrifying new order that has taken over the planet. On his journey through these four levels, he must avoid guards, destroy drones, collect lots of money, and upgrade his initially puny machine gun.