Murder on the Orient Express
The doctor watched him with great interest. He flattened out the two humps of wire, and with great care wriggled the charred scrap of paper on to one of them. He clapped the other on top of it and then, holding both pieces together with the tongs, held the whole thing over the flame of the spirit lamp. (1.7.119)
"I thought there were no detectives on the train when it passed through Yugo-Slavia – not until one got to Italy."
"I am not a Yugo-Slavian detective, Madame. I am an international detective."
"You belong to the League of Nations?"
"I belong to the world, Madame," said Poirot dramatically. (2.7.78-81)
Poirot shook his head violently.
"That is just it – it is impossible – quite impossible – that an honourable, slightly stupid, upright Englishman should stab an enemy twelve times with a knife! Do you not feel, my friends, how impossible it is?"
"That is the psychology," said M. Bouc.
"And one must respect the psychology. This crime has a signature and it is certainly not the signature of Colonel Arbuthnot." (2.8.118-121)