A spine-chilling ghost story with a thrilling mystery at its heart, set on a wild island off the coast of Scotland.

Alone in the world, Elspeth Swansome takes up the position of nanny on a remote Scottish island. Her charge, Mary, is distracted, secretive - and hasn't uttered a word since the death of her twin, William, just days after their former nanny disappeared. No one can say what happened to William. Just as no one can explain the lullabies sung in empty corridors. Nor the whistling that comes in the night...

Winter draws in. Passage to the mainland becomes impossible. Elspeth finds herself trapped.