The shade of Hettie Daynes

If you expect to see a ghost, you see a ghost ... That's what Bethan tells herself when her brother Harry takes her to see the ghost at the old reservoir. But she really can see it: a pale figure floating over the water, one finger pointing downwards. Local legend says that the ghost is the shade of Hettie Daynes, and ancestor of their family, who vanished over a hundred years ago. If so, what does she want? And why is she appearing now?