By the Pricking of My Thumbs (Tommy and Tuppence Series)

When Tommy and Tuppence visit an elderly aunt in her gothic nursing home, they think nothing of her mistrust of the doctors; after all, Ada is a very difficult old lady.

But when Mrs. Lockett mentions a poisoned mushroom stew and Mrs. Lancaster talks about "something behind the fireplace," Tommy and Tuppence find themselves caught up in a spine-chilling adventure that could spell death for either of them . . .