Vanishing Point - Miss Silver #25.
Vanishing Point first published in 1953.
When a girl goes out for a walk in Hazel Green and disappears, there are suspicions that her disappearance linked to security leaks at the nearby Air Ministry experimental station. Luckily, Miss Silver is at hand to find out.
Nothing much ever seemed to happen in the sleepy village of Hazel Green apart from the occasional tea-party, spiced with local gossip. Until Maggie Bell went out one evening for a breath of fresh air and never came back. Could Maggie's disappearance be linked to security leaks at the nearby Air Ministry? Or a sinister scheme being hatched closer to home? Miss Silver called in to solve the mystery just as a second person goes missing ...
Patricia Wentworth - born Dora Amy Elles - a British crime fiction writer.
She wrote a series of 32 classic-style whodunnits featuring Miss Silver. The first of which published in 1928, and the last in 1961, the year of her death.
Miss Silver, a retired governess-turned private detective, sometimes compared to Jane Marple, the elderly detective created by Agatha Christie. She works closely with Scotland Yard, especially Inspector Frank Abbott and is fond of quoting the poet Tennyson.
Wentworth also wrote 34 books outside of that series. Her novels were the topic of Jariel D. O'Neil's 1988 doctoral dissertation.