The Folk Keeper / Franny Billingsley.
Orphaned Corinna disguises herself as a boy to pose as a Folk Keeper, one who keeps the Evil Folk at bay, and discovers her heritage as a seal maiden when she is taken to live with a wealthy family in their manor by the sea.
New York :
Atheneum Books for Young Readers,
Walker Library - Curriculum Collection - Juvenile - 3rd Floor
Pull and Hold