After an unforeseen accident on the road, Amethyst the Changeling (Known to his friends as ACE the unicorn) is separated from his lover Lilly and the rest of his friends. He finds himself on a rock farm owned by the Pie sisters, Blinkie Pie and her older sister Inkie. ACE's friends locate him, only to find out that ACE has made a promise to Inkie that prevents him from leaving the farm. Ultimately calling into question his love for Lilly.