I found out about 13 Treasures by Michelle Harrison by way of Swan Bones, the blog of its illustrator Kelly Louise Judd, who I’ve long adored. Realizing it was probably a Girls Underground story was icing on the cake. But it turns out this one is a bit tricksy as far as the archetype goes. While it seems to be a pretty typical GU plot at first, the adversary is not revealed until the very end, and actually, I think one of the companions’ side story is a more clear-cut example of the archetype than the main character’s.
Tanya is 13, and she has been able to see fairies her whole life, fairies who quite constantly torment her. Due to their antics, she is seen as a difficult child, and her mother sends her to live with her grandmother one summer as a punishment (her father is totally absent). At her grandmother’s old mansion in the English countryside, Tanya discovers a dark secret about her family’s past, and find out that children have been going missing from the nearby village. With her dog and the groundskeeper’s son Fabian, Tanya begins to unravel the mystery of her true identity. She is helped along the way by an old gypsy woman. Tanya and her companions discover that a girl missing for 50 years is actually trapped in fairyland, and try to rescue her.
At one point Tanya ventures into a secret passage underground, and finds a girl hiding there, who is trying to rescue her own baby brother from the fairies. While it seems this girl Red is simply a supporting character, when the adversary is finally revealed and the confrontation happens, it is Red who ends up saving Tanya, and facing the adversary.
There are two more books in this series, and from what I can tell, Red remains a crucial character, perhaps even making the stories overall more about her than about Tanya, though it looks like Tanya might turn the tables and have to rescue Red in the end. I will hopefully have a chance to read them soon.