By the Pricking of My Thumbs

When Tommy and Tuppence Beresford visit Tommy's elderly Aunt Ada at the home for elderly ladies, she greets them by complaining. Because she is ordinarily cranky and difficult, they pay no attention. A few weeks later, Aunt Ada dies peacefully in her sleep. But, when another old lady vanishes soon afterward from the same nursing home, intrepid sleuth Tuppence senses that something is amiss, and she investigates. She begins with a single clue: a painting, given to Aunt Ada only days before her death, of a house by a canal. Tuppence's inquiries lead her to a missing tombstone, a mysterious house, and black magic - and danger!