Twenty years after a devastating alien invasion, Earth has harnessed the technology from the leftover extraterrestrial weaponry to build a global defense system. Humankind stands united through the Earth Space Defense (ESD), an organization formed to prepare for the extraterrestrial threat they fear will return. As the Fourth of July approaches, celebrations are on the horizon, but so is a new, more formidable alien menace. Visionary scientist David Levinson, now the ESD's Director, investigates a series of unusual phenomena at space outposts. The world soon realizes that these disturbances are precursors to an impending alien attack.

The returning alien invaders bring with them a colossal mother ship that begins its assault on Earth, producing gravity-defying destruction and overwhelming the planet's defenses. With the help of former President Whitmore, fighter pilot Captain Dylan Hiller, and a brave group of pilots and soldiers, humanity must use all the knowledge and technology at their disposal to prevent the total annihilation of their world. They face a battle against time itself, as the alien forces are bent on extinguishing human life for good, aiming to harvest Earth's resources. The fate of the world rests on the shoulders of these unlikely heroes as they orchestrate a global counterattack, the success of which will determine the survival of the human species.