Katherine shuddered, and he turned at once to her kindly.

"You must not let me distress you. Mademoiselle," he said. "To you this is all very new and terrible. To me, alas! it is an old story. One moment, I pray of you both."

They stood against the door watching him as he went quickly round the compartment. He noted the dead woman's clothes neatly j°^ed on the end of the berth, the big fur coat that hung from a hook, and the little red lacquer hat tossed up on the rack. Then he passed through into the adjoining compartment, that in which Katherine had seen the maid sitting. Here the berth had not been made up. Three or four rugs were piled loosely on the seat; there was a hat-box and a couple of suit-cases. He turned suddenly to Katherine.

"You were in here yesterday," he said. "Do you see anything changed, anything missing?"

Katherine looked carefully round both compartments.

"Yes," she said, "there is something missing-a scarlet morocco case. It had the initials 'R. V. K' on it. It might have been a small dressing-case or a big jewel-case.

When I saw it, the maid was holding it."

"Ah!" said Poirot.

"But, surely," said Katherine. "I-of course, I don't know anything about such things, but surely it is plain enough, if the maid and the jewel-case are missing?"

"You mean that it was the maid who was the thief? No, Mademoiselle; there is a very good reason against that."

"What?"

"The maid was left behind in Paris."

He turned to Poirot.

"I should like you to hear the conductor's story yourself," he murmured confidentially. "It is very suggestive."

"Mademoiselle would doubtless like to hear it also," said Poirot. "You do not object, Monsieur le Commissaire?"

"No," said the Commissary, who clearly did object very much. "No, certainly, M. Poirot, if you say so. You have finished here?"

"I think so. One little minute."

He had been turning over the rugs, and now he took one to the window and looked at it, picking something off it with his fingers.

"What is it?" demanded M. Caux sharply.

"Four auburn hairs." He bent over the dead woman. "Yes, they are from the head of Madame."

"And what of it? Do you attach importance to them?"

Poirot let the rug drop back on the seat.

"What is important? What is not? One cannot say at this stage. But we must note each little fact carefully."

They went back again into the first compartment, and in a minute or two the conductor of the carriage arrived to be questioned.

"Your name is Pierre Michel?" said the Commissary.

"Yes, Monsieur le Commissaire."

"I should like you to repeat to this gentleman"-he indicated Poirot-"the story that you told me as to what happened in Paris."

"Very good, Monsieur le Commissaire. It was after we had left the Gare de Lyon I came along to make the beds, thinking that Madame would be at dinner, but she had a dinner-basket in her compartment. She said to me that she had been obliged to leave her maid behind in Paris, so that I only need make up one berth. She took her dinnerbasket into the adjoining compartment, and sat there while I made up the bed; then she told me that she did not wish to be wakened early in the morning, that she liked to sleep on. I told her I quite understood, and she wished me 'goodnight'."

"You yourself did not go into the adjoining compartment?"

"No, Monsieur."

"Then you did not happen to notice if a scarlet morocco case was amongst the luggage there?"

"No, Monsieur, I did not."

"Would it have been possible for a man to have been concealed in the adjoining compartment?"

The conductor reflected.

"The door was half open," he said. "If a man had stood behind that door I should not have been able to see him, but he would, of course, have been perfectly visible to Madame when she went in there."

"Quite so," said Poirot, "Is there anything more you have to tell us?"

"I think that is all, Monsieur. I can remember nothing else."

"And now this morning?" prompted Poirot.

"As Madame had ordered, I did not disturb her. It was not until just before Cannes that I ventured to knock at the door. Getting no reply, I opened it. The lady appeared to be in her bed asleep. I took her by the shoulder to rouse her, and then-"

"And then you saw what had happened," volunteered Poirot. "Tres bien. I think I now all I want to know."

"I hope. Monsieur le Commissaire, it is not that I have been guilty of any negligence," said the man piteously. "Such an affair to happen on the Blue Train! It is horrible."

"Console yourself," said the Commissary.

"Everything will be done to keep the affair as quiet as possible, if only in the interests of justice. I cannot think you have been guilty of any negligence."

"And Monsieur le Commissaire will report as much to the Company?"

"But certainly, but certainly," said M. Caux impatiently. "That will do now."

The conductor withdrew.

"According to the medical evidence," said the Commissary, "the lady was probably dead before the train reached Lyons. Who then was the murderer? From Mademoiselle's story, it seems clear that somewhere on her journey she was to meet this man of whom she spoke. Her action in getting rid of the maid seems significant. Did the man join the train at Paris, and did she conceal him in the adjoining compartment? If so, they may have quarrelled, and he may have killed her in a fit of rage. That is one possibility.

The other, and the more likely to my mind, is that her assailant was a train robber travelling on the train, that he stole along the corridor unseen by the conductor, killed her, and went off with the red morocco case which doubtless contained jewels of some value. In all probability he left the train at Lyons, and we have already telegraphed to the station there for full particulars of any one seen leaving the train."

"Or he might have come on to Nice," suggested Poirot.

"He might," agreed the Commissary, "but that would be a very bold course."

Poirot let a minute or two go by before speaking, and then he said:

"In the latter case you think the man was an ordinary train robber?"

The Commissary shrugged his shoulders.

"It depends. We must get hold of the maid. It is possible that she has the red morocco case with her. If so, then the man of whom she spoke to Mademoiselle may be concerned in the case, and the affair is a crime of passion. I myself think the solution of a train robber is the more probable. These bandits have become very bold of late."

Poirot looked suddenly across to Katherine.

"And you. Mademoiselle," he said, "you heard and saw nothing during the night?" "Nothing," said Katherine.

Poirot turned to the Commissary.

"We need detain Mademoiselle no longer, I think," he suggested.

The latter nodded.

"She will leave us her address?" he said.

Katherine gave him the name of Lady Tamplin's villa. Poirot made her a little bow.

"You permit that I see you again, Mademoiselle?" he said. "Or have you so many friends that your time will be all taken up?"

"On the contrary," said Katherine, "I shall have plenty of leisure, and I shall be very pleased to see you again."

"Excellent," said Poirot, and gave her a little friendly nod. "This shall be a 'Roman Policier" a nous. We will investigate this affair together."