The intense interest aroused in the public by what was known at the time as “The Styles Case” has now somewhat subsided. Nevertheless, in view of the world-wide notoriety which has attended it, I have been asked… to write an account of it.
It might be the beginning of another Sherlock Holmes story, and certainly sounds like Watson narrating, but it is not. Even though it is narrated by one Hastings about his mercurial detective friend who investigates the body in the room locked from the inside problem with a string of apparently unrelated clues, still it is not Doyle. It is the first line of the first book by Agatha Christie—The Mysterious Affair at Styles—and her deductive detective is Belgian, but otherwise Holmesian in every respect. It is not so much an imitation as a simple continuance of the line created by Doyle, and before him Poe. In fairness to Agatha, on the seventh page the following lines occur—Hastings is questioned about his ambitions by the lady of the manor.
"Well, I’ve always had a secret hankering to be a detective!”
“The real thing—Scotland Yard? Or Sherlock Holmes?”
“Oh, Sherlock Holmes by all means. But really, I am awfully drawn to it. I came across a man in Belgium once, a very famous detective, and he quite inflamed me.”
    Thus was the investigative career of Hercule Poirot launched. Interestingly, it was written in 1920, seven years before Doyle published The Case Book of Sherlock Holmes—the final volume that he was reluctantly forced to write by the sheer weight of popular demand. In this weird way, the Victorian Age and Modern Times overlapped, and what went before still prevailed when what came after was already begun.
Ten little nigger boys went out to dine;
One choked his little self and then there were nine.
    Agatha Christie, as she proceeded, tried to squeeze everything she could out of her chosen formula. This one, The Ten Little Niggers, written in 1939, has the novelty that all of the characters are murdered, each by means reflected in the nursery rhyme,  thereby eliminating all possible suspects, not to mention also liquating the potential hero and the very murderer themselves.  
One little nigger boy left all alone;
He went and hanged himself and then there were none.
    Very clever contrivance, but the book became even more fascinating when the US thought-police concluded the use of the word Nigger in the title offensive to negroes, which word itself would soon become offensive to Afro-Americans. So they changed it to The Ten Little Indians, an alternative version of the poem. Alas, before long the indigenous Americans reckoned they were no less offended than the negroes. So, in a later edition still, they took the last line of the rhyme instead And Then There Were None, which of course was the point of the title in the first place, but less subtle. But finally, once they discovered that no one would allow the use of the word nigger to be changed in Tom Sawyer, the counter-thought-police prevailed, and the book was restored to its original title. Christie’s idea of killing everyone involved was perhaps a great idea in more ways than one.
    In her quest to write increasingly baffling murder mysteries, Agatha Christie hit something of a peak with Murder on the Orient Express. In the Ten Little Niggers, she worked the trick where all of the characters are murdered, leaving no one left alive to have done the killing. In Orient Express (I won’t give the answer away in case you come from another planet and therefore haven’t heard it), suffice to say she works a similar trick in reverse. The pinnacle of her ingenuity.