M. Bouc was handling the button Mrs. Hubbard had left behind her.

"That button, it suggests possibilities," said Poirot thoughtfully. "Let us interview next the Swedish lady before we discuss the evidence we have heard."

M. Bouc gave directions to the restaurant attendant, and presently the lady with the yellowish-grey bun of hair and the long mild sheep-like face was ushered in. She peered shortsightedly at Poirot through her glasses, but was quite calm.

"This button. I cannot understand it. Does it mean that, after all, Pierre Michel is involved in some way?" he said. He paused, then continued, as Poirot did not reply. "What have you to say, my friend?"

She was, she told him, matron in a missionary school near Stamboul. She was a trained nurse.

It transpired that she understood and spoke French, so that the conversation took place in that language. Poirot first asked her the questions to which he already knew the answers -- her name, age, and address. He then asked her her occupation.

He sorted through the pile of passports in front of him. "Ah! here we are. Greta Ohlsson, age forty-nine."

"I do not know. It may be so. I opened the door of his compartment by mistake. I was much ashamed. It was a most awkward mistake."

"And was it?"

"He laughed and said a few words. I -- I did not quite catch them."

"Yes."

"Yes. He was reading a book. I apologized quickly and withdrew."

"Did he say anything to you?"

"And what did you do after that, Mademoiselle?" asked Poirot, passing from the subject tactfully.

"Did she ask you whether the communicating door between her compartment and that of M. Ratchett was bolted?"

"Naturally. It is very dreadful. And the American lady tells me that the murderer was actually in her compartment."

A slight flush showed on the worthy lady's cheek.

"After that I go back to my own compartment, I take the aspirin and lie down."

"I hear, Mademoiselle, that you were the last person to see the murdered man alive?"

"And after that?"

"I went in to the American lady, Mrs. Hubbard. I asked her for some aspirin and she gave it to me."

"You actually saw him?"

"Yes."

"You know, of course, of what took place last night, Mademoiselle?"

"The lower berth, No. 10."

"That would be Vincovci. Now your compartment, Mademoiselle, is this one?" he indicated it on the plan.

"Not until this morning."

"After the train left Vincovci, did she leave the compartment?"

"I sleep very lightly. I am used to waking at a sound. I am sure if she had come down from the berth above I would have awakened."

"No, I am sure she did not."

"Not very quickly. My head got better, but I lay awake some time."

"You had the upper or the lower berth?"

"When I got into bed it was five minutes to eleven, because I look at my watch before I wind it up."

"What time was all this?"

"Did you yourself leave the compartment?"

"I do not think so. We stopped, I think, at a station, just as I was getting drowsy."

"Had the train come to a stop before you went to sleep?"

"Yes, a young English lady. Very nice, very amiable. She had travelled from Baghdad."

"And you had a companion?"

"That is so, yes."

"Why are you sure if you were asleep?"

"Have you a scarlet silk kimono, Mademoiselle?"

"Did you go to sleep quickly?"

She took the paper and pencil he gave her and wrote down the name and address as requested.

"Do you remember hearing of the Armstrong kidnapping case?"

"No, what was that?"

"Yes, I am going home for a holiday. But first I go to Lausanne to stay with a sister for a week or so."

Greta Ohlsson was indignant. Her yellow bun of hair quivered with her emotion.

"And the one you live with, Miss Debenham? What color is her pajamas?"

"With pleasure."

"Have you ever been in America, Mademoiselle?"

"Perhaps you will be so amiable as to write me down the name and address of your sister?"

Poirot nodded. Then he said in a friendly tone: "Why are you taking this journey? A holiday?"

"A pale mauve abba such as you buy in the East."

"No. Very nearly once. I was to go with an invalid lady, but it was cancelled at the last moment. I much regretted. They are very good, the Americans. They give much money to found schools and hospitals. They are very practical."

Poirot explained.

"No, indeed. I have a good comfortable dressing gown of Jaeger material."

"That is very clear," he said.

About 10:00 MacQueen leaves Ratchett.

"Mon cher, it is my habit to be neat and orderly. I make here a little table of chronological events."

About 1:17 Mrs. Hubbard thinks man is in her carriage. Rings for conductor.

Poirot was writing busily on a sheet of paper.

He finished writing and passed the paper to M. Bouc.

9:15 Train leaves Belgrade.

About 10:40 Greta Ohlsson sees Ratchett (last seen alive). N. B.-- He was awake reading a book.

"There is nothing there that strikes you as at all odd?"

"What is it you write there, my friend?" asked M. Bouc.

0:10 Train leaves Vincovci (late).

M. Bouc nodded approval.

The amiable Swede departed, her kindly face flushed, her eyes suffused with tears.

0:37 Ratchett's bell rings. Conductor answers it. Ratchett says, "Ce n'est rien. Je me suis trompé."

"That there are in the world such evil men! It tries one's faith. The poor mother. My heart aches for her."

0:30 Train runs into a snowdrift.

About 9:40 Valet leaves Ratchett with sleeping draught beside him.

"Without a doubt, that is the solution of the mystery. Doubtless he and this Ratchett were in this kidnapping business together. Cassetti is an Italian name. In some way Ratchett did on him what they call the double-cross. The Italian tracks him down, sends him warning letters first, and finally revenges himself upon him in a brutal way. It is all quite simple."

"No, it seems all quite clear and above board. It seems quite plain that the crime was committed at 1:15. The evidence of the watch shows us that, and Mrs. Hubbard's story fits in. For my mind, I will make a guess at the identity of the murderer. I say, my friend, that it is the big Italian. He comes from America -- from Chicago -- and remember an Italian's weapon is the knife, and he stabs not once but several times."

"Me, I am convinced it is the truth," said M. Bouc, becoming more and more enamoured of his theory.

"That is true."

Poirot shook his head doubtfully.

"It is hardly as simple as that, I fear," he murmured.

"And what about the valet with the toothache who swears that the Italian never left the compartment?"

Poirot twinkled.

"That is the difficulty."

"Yes, it is annoying, that. Unlucky for your theory, and extremely lucky for our Italian friend that M. Ratchett's valet should have had the toothache."

"It will be explained," said M. Bouc with magnificent certainty.

"No, it is hardly so simple as that," he murmured again.

Poirot shook his head again.