Heart and her winged, clockworks horse, Equuleus, land safely out of the clutches of on the 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 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— —shape-shifting young man appears on the scene to help Father Inventor save his world, while proclaiming an undying love for Heart.