Featuring Tommy and Tuppence Beresford.

"Tommy and Tuppence Beresford, once the 'Young Adventurers', later functioning as 'Blunt's Brilliant Detectives', finally active in the Second War tracking down that notorious spy 'N or M', are now living in peaceful retirement - they lead a happy life...
What more can they want?
Well-?
They go to visit an elderly relative, Tommy's Aunt Ada who is established in Sunny Ridge, well-run home for Elderly Ladies - on the surface it appears to be a model of its kind. But is it?
Aunt Ada dies peacefully in her bed, but another old lady leaves very suddenly in the care of somewhat mysterious relatives.
Tuppence has her misgivings - Tommy starts by pooh-poohing them. But Tuppence makes up her mind that she will discover what has really happened to old Mrs. Lancaster.
The hunt involves an oil painting of a house by a canal, a peaceful village where nothing ever happens(?), a character whom Tuppence christens 'the friendly witch', a hunt through old tombstones in a churchyard, and, when Tommy returns from a hush-hush conference, he finds that Tuppence has failed to return from her quest.
Brilliantly sustained mystery is always to be found in a novel by Agatha Christie, but her latest story contains an extra element, and might equally well have been entitled 'By the Chilling of Your Spine'." -- Inside cover.