I started writing Kristina (which was supposed to be mostly light and fun, with some drama thrown in), and then out of the blue got this big serious impulse, which led me to write Phantoms of the Past. POTP *was* a serious story, and it did derail Kristina for some time, but it definitely was a case where I felt I "had" to write POTP, to get the Phantom "seriousness" out of my system.