Patricia A. McKillip 
Bell at Sealey Head [EPUB ebook] 

Sealey Head is a small town on the edge of the ocean, a sleepy place where everyone hears the ringing of a bell no one can see. On the outskirts of town is an impressive estate, Aislinn House, where the aged Lady Eglantyne lies dying, and where the doors sometimes open not to its own dusty rooms, but to the wild majesty of a castle full of knights and princesses …