Diamond Tiara has reformed herself into a far better pony, much to everyone's joy. Everyone except her mother. Now, she faces the horror of spending most of Hearth's Warming Eve completely alone, while she puzzles out a problem that no foal should have to solve. When Starlight Glimmer stumbles across her, they both realise that Hearth's Warming is not just about old connections and by bringing old and new together they can start to mend what is broken and find what is missing.