Princess Luna's sister and son urge her to take a night off, or at least get some sleep, and her son attends The Grand Galloping Gala in her stead.
Someone's gotta represent the Lunar family.
He just has a few problems. As he reminisces about the things he can't get back, and the things he never even knew, he comes to recall the mixed life he's led thus far, and imagine the life he'll lead in the future.

Rated Teen because Nightsong still remembers being turned into a changeling quite vividly, and also thinks about how he and his adopted sister once... They were under both a love and a lust spell at the time.