A discussion of murder mysteries on Twitter included this claim:
Agatha Christie is on record as saying that she didn’t decide who the murderer was until she was ready to write the last chapter—then she would go back through all the previous chapters making any necessary changes.
Q T Arbuthnot (9th October 2021). twitter.com.
Is Christie really “on record” as saying this? If not, is there another, less famous, writer of detective stories who did say something like this, who might have been misremembered as Christie?
I find the the claim hard to believe of Christie. Her plots are usually too tightly constructed for it to be possible to switch the murderer merely by rearranging the clues. There is often a plot device that simultaneously conceals the murderer and structures the events of the novel, so that the plot must have been worked out, at least in outline, before starting to write. She says in her autobiography that plot comes first:
Plots come to me at such odd moments; when I am walking along a street, or examining a hat shop with particular interest, suddenly a splendid idea comes into my head, and I think, “Now that would be a neat way of covering up the crime so that nobody would see the point.” Of course, all the practical details are still to be worked out, and the people have to creep slowly into my consciousness, but I jot down my splendid idea in an exercise book.
Agatha Christie (1977). An Autobiography, pp. 423–424. New York: Dodd, Mead.
However, the claim might be true of some other writer, whose plots are less tightly constructed.