The Lighthouse Witches by C J Cooke

On the island of Lon Haven off the Scottish coast stands an old, decommissioned lighthouse. This was in its turn built on the remains of an ancient broch underneath which lay a cave where, during the 1600s, women accused of witchcraft were imprisoned awaiting trial and execution. It's a place the locals fear, and keep well clear of, but now (1998) it's been bought, and the new owner has employed an artist to help turn the forbidding tower into a writer's studio. 

Liv Stay doesn't believe in witches or ghosts, but there's certainly something spooky about the lighthouse she's been commissioned to paint. She's barely settled into the adjacent cottage before strange things start to occur, and within months her and two of her daughters have disappeared, like so many islanders before them. The surviving daughter, Luna, has spent her life moving between foster homes, keeping well away from Lon Haven, trying to forget what happened there, but over 20 years later she's drawn back to the island when one of her sisters is found at last - but not having aged at all. 

I'm always on the look out for good supernatural stories, and I thought from what I'd heard online that this would be one, but overall I feel it disappointed.

It starts excellently. The author builds up the atmosphere of strange goings-on, of sightings of a small unknown child, of possible tell-tale signs of witchcraft activity gradually and carefully - enough to keep the reader intrigued; not so much that it seems completely over the top. The island's inhabitants tell of dreadful things happening in the past - the disappearance of children and their replacement by changelings - and hint that it still happens. It's enthralling; very dark and gothic, mixing terror and superstition.

But then - half, maybe three-quarters, of the way though I realised what the plot twist was, and from then I just wanted the characters to hurry up, see what was obvious to me, and solve the mystery. A bit like guessing the murderer in a whodunnit, it took the edge of the latter part of the book.