Spensa's world has been under attack for hundreds of years. An alien race called the Krell leads onslaught after onslaught from the sky in a never-ending campaign to destroy humankind. Humanity's only defense is to take to their ships and fight the enemy in the skies. Pilots have become the heroes of what's left of the human race. Spensa has always dreamed of being one of them, of soaring above Earth and proving her bravery. But her fate is intertwined with her father's - a pilot who was killed ...