A thousand and 24 years ago, Luna got banished to the moon 'permanently' when she became Nightmare Moon. Eternity alone was something that Luna wasn't going to let happen, so after a thousand years of effort, she finally escaped, but at a grave cost.

That was 21 years ago. By now, she has been adopted by a nice family and lives as one of their own, but as the 1000th summer's sun celebration arrives, she is forced to face her past.

Meanwhile, Twilight has to deal with this pretty pony that she initially dreaded the arrival of, and Princess Celestial has to destroy 1000 years of attempts of moving on when her sister is back.