"I was searching for a flaw, my friend."

M. Bouc was looking at his friend curiously.

"I do not quite understand you, mon vieux. You were trying to do -- what?"

"You suspect her," said M. Bouc slowly. "But why? She seems a very charming young lady -- the last person in the world to be mixed up in a crime of this kind."

"I agree," said Constantine. "She is cold. She has not emotions. She would not stab a man; she would sue him in the law courts."

"A flaw?"

"Yes -- in the armour of a young lady's self-possession. I wished to shake her sangfroid. Did I succeed? I do not know. But I know this -- she did not expect me to tackle the matter as I did."

Poirot sighed "You must, both of you, get rid of your obsession that this is an unpremeditated and sudden crime. As for the reason why I suspect Miss Debenham, there are two. One is because of something that I overheard, and that you do not as yet know."

He retailed to them the curious interchange of phrases he had overheard on the journey from Aleppo.

"That is curious, certainly," said M. Bouc when he had finished. "It needs explaining. If it means what you suspect it means, then they are both of them in it together -- she and the stiff Englishman."

"You said there was another reason for your suspicions of her," M. Bouc reminded him.

Poirot nodded.

Poirot smiled.

"And that is just what is not borne out by the facts," he said. "See you, if they were both in this together, what should we expect to find -- that each of them would provide an alibi for the other. Is not that so? But no -- that does not happen. Miss Debenham's alibi is provided by a Swedish woman whom she has never seen before, and Colonel Arbuthnot's alibi is vouched for by MacQueen, the dead man's secretary. No, that solution of the puzzle is too easy."

M. Bouc shook his head. "I think you are wrong, my friend. I do not see that young English girl as a criminal."

"Ah! but that is only psychological. I ask myself, is it possible for Miss Debenham to have planned this crime? Behind this business, I am convinced, there is a cool, intelligent, resourceful brain. Miss Debenham answers to that description."

"Ah, well," said Poirot, picking up the last passport, "to the final name on our list. Hildegarde Schmidt, lady's maid."

Summoned by the attendant, Hildegarde Schmidt came into the restaurant car and stood waiting respectfully.

She did so, folding her hands and waiting placidly till he questioned her. She seemed a placid creature altogether -- eminently respectable -- perhaps not over intelligent.

Poirot motioned her to sit down.

Poirot's methods with Hildegarde Schmidt were a complete contrast to his handling of Mary Debenham.

He was at his kindest and most genial, setting the woman at her ease. Then, having got her to write down her name and address, he slid gently into his questions.

The interview took place in German.

"We want to know as much as possible about what happened last night," he said. "We know that you cannot give us much information bearing on the crime itself, but you may have seen or heard something that, while conveying nothing to you, may be valuable to us. You understand?"

She did not seem to. Her broad, kindly face remained set in its expression of placid stupidity as she answered:

"I do not know anything, Monsieur."

"I do not, Monsieur. I was asleep, you see, when the attendant came and told me."

"Eh bien, then, you received the summons and you got up. Did you put on a dressing gown?"

She stared at him. "It is a dark-blue flannel dressing gown, Monsieur."

"Yes, yes. Was it usual for you to be sent for in this way?"

"It was not unusual, Monsieur. The gracious lady often required attention at night. She did not sleep well."

"That, yes."

"No, Monsieur, I put on a few clothes. I would not like to go in to her Excellency in my dressing gown."

"And yet it is a very nice dressing gown -- scarlet, is it not?"

"Well, for instance, you know that your mistress sent for you last night?"

"I gave her massage, Monsieur, and then I read aloud. I do not read aloud very well, but her Excellency says that is all the better. So it sends her better to sleep. When she became sleepy, Monsieur, she told me to go, so I closed the book and I returned to my own compartment."

"Ah! continue. A little pleasantry on my part, that is all. So you went along to Madame la Princesse. And what did you do when you got there?"

"Do you remember the time?"

"No, Monsieur."

"What was he doing?"

"He came out of one of the compartments, Monsieur."

"Well, how long had you been with Madame la Princesse?"

"You did not, for instance, see a lady in a scarlet kimono with dragons on it?"

"And you met no one in the corridor?"

"And then?"

Hildegarde Schmidt looked frightened again and Poirot cast a reproachful glance at his friend.

"There is nothing more, Monsieur. I returned to my carriage and went to sleep."

"No, Monsieur."

"First, I fetched her Excellency an extra rug from my compartment. It was very cold in spite of the heating. I arranged the rug over her and she wished me good night. I poured her out some mineral water. Then I turned out the light and left her."

"But you did see the conductor?"

Her mild eyes bulged at him. "No, indeed, Monsieur. There was nobody about except the attendant. Everyone was asleep."

"Yes, Monsieur."

"About half an hour, Monsieur."

"Do you know what time that was?"

"Good, continue."

"What?" M. Bouc leaned forward. "Which one?"

"It was about the middle of the coach, Monsieur. Two or three doors from Madame la Princesse."

"Naturally," he said. "The conductor often has to answer bells at night. Do you remember which compartment it was?"

"Ah! tell us, if you please, exactly where this was and what happened."

"Towards me, Monsieur. He apologized and passed on down the corridor towards the dining car. A bell began ringing, but I do not think he answered it." She paused and then said: "I do not understand. How is it --?"

Poirot spoke reassuringly.

"And he came out of a compartment and almost collided with you? In which direction was he going?"

"It was not the same conductor who woke me, Monsieur. It was another one."

"He nearly ran into me, Monsieur. It was when I was returning from my compartment to that of the Princess with the rug."

"Ah, another one! Had you seen him before?"

"It is just a question of times," he said. "All a matter of routine. This poor conductor, he seems to have had a busy night -- first waking you and then answering bells."

Poirot was continuing his questions in an easy friendly manner.

"I think so, Monsieur."

"No. Monsieur."

Tears had come into the woman's eyes. Her strong motherly soul was moved.

"It was an abominable crime," said Poirot gravely.

He drew a scrap of cambric from his pocket and handed it to her.

"Ah! Do you think you would recognize him if you saw him?"

Poirot murmured something in M. Bouc's ear. The latter got up and went to the door to give an order.

"Yes, I have heard, Monsieur. It was abominable -- wicked. The good God should not allow such things. We are not so wicked as that in Germany."

"You have heard, perhaps, of who this man who was killed really was -- that he was responsible for the death of a little child."

"Never, Monsieur. It must be a fine country."

"Have you ever been to America, Frau Schmidt?"

"Is this your handkerchief, Frau Schmidt?"

There was a moment's silence as the woman examined it. She looked up after a minute. The colour had mounted a little in her face.

"Ah! no, indeed. It is not mine, Monsieur."

"It is not yours and you do not know whose it is?"

"I? Oh, no, Monsieur."

Hildegarde Schmidt looked at them and immediately shook her head.

The three men entered. Pierre Michel, the big blond conductor of the Athens-Paris coach, and the stout burly conductor of the Bucharest one.

M. Bouc whispered in his ear. Poirot nodded and said to the woman: "The three sleeping car attendants are coming in. Will you be so kind as to tell me which is the one you met last night as you were going with the rug to the Princess?"

"It has the initial H, you see. That is why I thought it was yours."

Of the three listening, only Poirot caught the nuance of hesitation in the reply.

"Ah! Monsieur, it is a lady's handkerchief, that. A very expensive handkerchief. Embroidered by hand. It comes from Paris, I should say."

"No, Monsieur," she said. "None of these is the man I saw last night."

"But these are the only conductors on the train. You must be mistaken."

"I am quite sure, Monsieur. These are all tall, big men. The one I saw was small and dark. He had a little moustache. His voice when he said 'Pardon' was weak like a woman's. Indeed, I remember him very well, Monsieur."