Cloudsdale was at its peak of production, from rainbows to clouds and snowflakes and every shade of weather between. However, in the midst of their finest hour, the factory producing rainbows explodes, and with it, the other factories. Many pegasi were injured in the explosion, even the Wonderbolts won't fly for a long time after this. What will become of Cloudsdale, is far too terrifying to imagine.

The story is told in the point of view of Nurse Redheart, as she investigates the not-so-normal-for-an-explosion-injuries. Mysterious, fresh injuries on pegasus ponies continue to appear, even as they are hospitalized.

Luna and Celestia, as two fillies, have frolicked happily and free of responsibility for far too long. Now, they shall up bring four foals that will one day rule the weather and season of Equestria. Under Luna, there are the seasons with an abundance of night; Autumn and Winter. Under Celestia there are the warmer seasons; Spring and Summer. These are the sweetest souls ever in existence. But what will happen when Celestia becomes much like her father, and seeks to control when and where the seasons are and what they do, will be far worse than ever expected. When the four seasons are kept apart, all is lost.