This is a pretty, pretty little prologue of a tale, set in the Days Long Past, many a year before a girl called September came along and became The Girl Who Circumnavigated Fairyland in a Ship of Her Own Making.
If you've never read the series before, this could be a good place to start, to see if you like C.M. Valente's style. I personally think it is a hit-or-miss, as she sometimes waxes lyrical for paragraphs on end, and while it is very pretty indeed, sometimes it lacks substance. Take for instance this novelette, it began with 4 paragraphs and 3 lines that tells you nothing at all, before the story properly starts.
For those with knowledge of Mallow's eventual fate , this is heart-breaking. Not a spoiler, by the way - you can surmise that much, I'm sure, from the title.