In the far future, Princess Twilight proposes a grand scale project to resolve Equestria's looming energy crisis once and for all. Two retired princesses have some personal issues with this.
Luna is a strange mare. Cadance is only now just starting to see how strange she is when Luna mentions the unthinkable. Maybe she'll learn something new in the process.
How is a proper princess supposed to deal with a visible expression of public disapproval? Well, she isn't in Zephyr Heights any more, so summary execution is probably out...