Twelve years ago Flora's mother Ingrid disappeared, vanishing from a Dorset beach. Everyone - especially her sister and father Gil - believes Ingrid is long dead. Everyone that is except Flora. So when she hears that her father has had an accident and is insisting that he saw his wife, Flora rushes home.

But the answers Flora seeks are nowhere to be found - only further questions:

What are the mysterious letters Gil keeps referring to?
Why is the house filled with towering piles of books?
And who was it her father actually saw?

As Flora assembles the pieces of this puzzle the true and troubling portrait of her parents' extraordinary marriage is slowly revealed ...