What an incredibly powerful, creative, deeply-layered, convoluted, engrossing mystery! Ever since I read Agatha Christie's AND THEN THERE WERE NONE in childhood, I have adored the Locked-Room Mystery Concept. Here Author Alice Feeney frames it as an intermittently-inescapable tiny island as the "locked-environment," one from which escape is only possible by motorboat once the tide is high, not by rowboat or swimming or walking the causeway. Once you're on the island, you'll stay, until Low Tide.
Not an environment suitable for everyone, but for children's author/illustrator Beatrice Darker (Nana), who inherited Seaglass House (and tiny isle) from her mother, and for her youngest granddaughter, Daisy, it is ideal, and exceptionally special. For Daisy's mother Nancy, it's a sometime escape. For orchestra conductor Frank, son of Nana and Daisy's father, it's to be escaped, as it is for Daisy's older sisters, Rose and Lily.
Author Feeney delivers through the difficult lens of First-Person Narrative, operating through a truly Unreliable Narrator, likely the most stunning example of unreliability in narration I have ever encountered [ and if there's an example more so, please clue me in!]
I've often written of being blown away by a Denouement or Ending. In DAISY DARKER, there isn't a clever Hercule Poirot to elucidate the crimes, the causes, and the culprits. But the unfolding of this Denouement is without par, and I was speechless throughout.