Come to a Twilight World.... Heart and her winged, clockworks horse, Equuleus, land safely out of the clutches of The Purists on the little synthetic moon known simply as Pink, constructed by her father, Father Inventor, many years previous, where he escaped when banished from Earth. Heart and Equuleus are left to explore as her father becomes ever more engrossed in the creation of a shield to protect Pink from the rabid determination of The Purists to destroy the little moon and everything on it. Fearing that life on the eternally twilight moon may prove to be dangerously boring, Heart suddenly discovers that it's filled with mystery and intrigue and astonishingly more complicated than it first appears. As power plays augment on Earth with the threat of frightening repercussions for Pink, Xavier, a strange-yet beautiful!-shape-shifting young man appears on the scene to help Father Inventor save his world, while proclaiming his undying love for Heart.