By the Pricking of My Thumbs

Blurb

By The Pricking of My Thumbs is a work of detective fiction by Agatha Christie and first published in the UK by the Collins Crime Club in November 1968 and in the US by Dodd, Mead and Company later in the same year. The UK edition retailed at twenty-one shillings and the US edition at $4.95. It features her detectives Tommy and Tuppence Beresford.
Youthful in two Christie books written in the 1920s, middle-aged in a World-War II spy novel, and here elderly, Tommy and Tuppence were unusual in that they aged according to real time, unlike Hercule Poirot or Miss Marple, whose age remained more or less the same from their first novels in the 1920s, to their last novels in the 1970s.
The title of the book comes from Act 4, Scene 1 of William Shakespeare's Macbeth, when the second witch says:
By the pricking of my thumbs,
Something wicked this way comes.