Peter's sixteen year old sister Tara disappears while taking a walk among the Spring flowers and woods near her home. She returns on cold Christmas day twenty years later, cold, tired, dirty, and to all appearances not having aged in those twenty years. She claims to have spent those years (which to her were only 6 months) with the race of magical creatures that we would call Fairies, although we learn that they not only don't like that term, but that they are very physical and more dangerous and aggressive than we imagined.
Woven into a story that is both realistic as well as fantastic is the theme of the loss of youth and of time.
Yesterday I watched my grand-daughter play in my living room and I almost felt as if the fairies had worked some magic because it seems like yesterday that I listened to her mother speak her first words. They clearly have changed so much yet why do I feel that I have not? I didn't feel the rush of years---but I am sure that I look as changed to them as they do to me.
There is a rather sinister scene at the end of the book where we see that the Fairies will soon be after Peter's young daughter. It made me think that even as the Fairies have worked their magic and my little girl is now a mother, I will blink again and my grand-daughter will be a woman. And I will still wonder where it all went.