With her sister back and her niece's wedding not far off on the horizon, Celestia finds a strange letter in her room. A letter from a self-proclaimed Prince of Changelings, and he's asking for Equestria's help.
After decades of silent suffering, an unexpected event causes Luna to reach her breaking point much sooner. Instead of embracing her inner darkness, she makes a very different decision that will change her life in unimaginable ways.