It's a slow start, like many good stories, and it seems like its mystery shows its hand too soon. Stick with it, though, and you'll be rewarded with adventure and more mystery than you can carry.
A child slips through a portal into the land of the Fae and traverses the Otherworld with the help of a young elf, while her parents are left to deal with the changeling that was left in her place.
EDIT: Yeeeeep, you’re right.