White crow - Marcus Sedgwick

It's summer. Rebecca is an unwilling visitor to Winterfold - taken from the buzz of London and her friends and what she thinks is the start of a promising romance. Ferelith already lives in Winterfold - it's a place that doesn't like to let you go, and she knows it inside out - the beach, the crumbling cliff paths, the village streets, the woods, the deserted churches and ruined graveyards, year by year being swallowed by the sea. Against her better judgement, Rebecca and Ferelith become friends, and during that long, hot, claustrophobic summer they discover more about each other and about Winterfold than either of them really want to, uncovering frightening secrets that would be best left long forgotten.
Interwoven with Rebecca and Ferelith's stories is that of the seventeenth century Rector and Dr Barrieux, master of Winterfold Hall, whose bizarre and bloody experiments into the after-life might make angels weep, and the devil crow.