Persons Unknown — Gwen Moffat

Amateur detective Miss Pink is paying a visit to the remote Welsh village of Abersaint to join the 87th birthday celebrations of her old friend Roderick Bowen. He is still in full possession of his faculties, and has recently won a notable victory in a battle with the Atomic Energy Authority, who were planning to build a fast breeder reactor on his land.
But he has just had a nasty fall, down the granary steps, and believes that someone tried to kill him. Soon, too, Miss Pink has a possible murder to investigate: the mysterious death, in a fire, of Abersaint's most incongruous visitor, the flamboyant Sandra Maitland, shortly after she has gatecrashed Roderick's birthday party and has admitted to being a high-class callgirl, whose memoirs, now in manuscript, reveal her association with many prominent politicians.
Members of Roderick's family are in varying degrees under suspicion, notably his granddaughter Rachel, who avoids police questioning by vanishing to her secret hiding place on the cliffs -- which is know only to that other intrepid climber, Miss Pink, and possibly to a fourteen-year-old village lad, Jakey, a young monster who seems capable of any crime.