"I am not keeping back facts. Every fact that I know is in your possession. You can draw your own deductions from them."
Hercule Poirot
In October 1920.
Agatha Christie's first novel, The Mysterious Affair at Styles, appears in the U.S., introducing her long-running Belgian detective Hercule Poirot in the setting of an English country house.
https://en.wikipedia.org/wiki/The_Mysterious_Affair_at_Styles
The Mysterious Affair at Styles at PG:
https://gutenberg.org/ebooks/863