I learned (what I suppose I really knew already) that one can never go back, that one should not ever try to go back — that the essence of life is go… - Agatha Christie

"He dragged me back - just in time. A tree had crashed down on to the side walk, just missing us. Poirot stared at it, pale and upset.
"It was a near thing that! But clumsy, all the same - for I had no suspicion - at least hardly any suspicion. Yes, but for my quick eyes, the eyes of a cat, Hercule Poirot might now be crushed out of existence - a terrible calamity for the world. And you, too, mon ami - though that would not be such a national catastrophe."
"Thank you," I said coldly."

Give up the past! Turn to the future! What is done is done. Bitterness will not undo it.

And that very same evening - that very same evening - Lord Edgware dies. Good title that, by the way. Lord Edgware Dies. Look well on a book stall.