Twelve or thirteen miles from Souillac the main line from Brives to Cahors, which flanks the slope, describes a rather sharp curve. The journey is a particularly picturesque one, and travellers who make it during the daytime have much that is interesting and agreeable to see; but while they are admiring the country, which marks the transition from the severe region of the Limousin to the more laughing landscapes on the confines of the Midi, the train suddenly plunges into a tunnel which runs for half a mile and more through the heart of the mountain slope. Leaving the tunnel, the line continues along the slope, then gradually descends towards Souillac. Two or three miles from that little station, which is a junction, the line runs alongside the highroad to Salignac, skirts for a brief distance the CorrÈze, one of the largest tributaries on the right bank of the Dordogne, and then plunges into the heart of Lot.

Torrential winter rains had seriously affected the railway embankment, particularly near the mouth of the tunnel; a succession of heavy storms in the early part of December had so greatly weakened the ballast that the chief engineers of the Company had been hastily summoned to the scene of the mischief. The experts decided that very important repairs were required close to the Souillac end of the tunnel. It was necessary to put in a complete system of drainage, with underground pipes through which the water that came down from the mountain could escape between the ballast and the side of the rock and so pass underneath the permanent way. The sleepers, too, had been loosened by the bad weather, and some of them had perished so much that the chairs were no longer fast, a matter which was all the more serious because the line described a very sharp curve at that precise spot.

Gangs of first-class navvies had been hurriedly requisitioned, but in spite of the fact that an exceptional rate of wages was paid, a local strike had broken out and for some days all work was stopped. Gradually, however, moderate counsels prevailed and for over a week now, nearly all the men had taken up their tools again. Nevertheless, for a month past, these various circumstances had resulted in all the trains running between Brives and Cahors, being regularly half an hour late. Further, in view of the dangerous state of the line, all engine drivers coming from Brives had received orders to stop their trains two hundred yards from the end of the tunnel, and all drivers coming from Cahors to stop their trains five hundred yards before the entrance to the tunnel, so that should a train appear while any work was going on which rendered it dangerous to pass, it could wait until the work was completed. The order was also issued with the primary object of preventing the workers on the line from being taken by surprise.

Day was just breaking this grey December morning, when the gang of navvies set to work under a foreman, fixing on the down line the new sleepers which had been brought up the day before. Suddenly a shrill whistle was heard, and in the gaping black mouth of the tunnel the light of two lamps became visible; a train bound for Cahors had stopped in accordance with orders, and was calling for permission to pass.

The foreman ranged his men on either side of the down line and walked to a small cabin erected at the mouth of the tunnel, where he pulled the hand-signal so as to show the green light, thereby authorising the train to proceed on its way.

There was a second short, sharp whistle; heavy puffs escaped from the engine, and belching forth a dense volume of black smoke it slowly emerged from the tunnel, followed by a long train of carriages, the windows of which were frosted all over by the cold temperature outside.

A man approached the cabin allotted to the plate-layer in charge of that section of the line in which the tunnel was included.

"I suppose this is the train due at VerriÈres at 6.55?" he said carelessly.

"Yes," the plate-layer answered, "but it's late, for the clock down there in the valley struck seven several minutes ago."

The train had gone by: the three red lamps fastened at the end of it were already lost in the morning mist.

The man who spoke to the plate-layer was no other than FranÇois Paul, the tramp who had been discharged by the magistrate installed at the chÂteau of Beaulieu, at precisely the same time the day before, after a brief examination. In spite of the deep wrinkle furrowed in his brow the man seemed to make an effort to appear friendly and to want to carry on the conversation.

"There aren't many people in this morning train," he remarked, "specially in the first-class carriages."

The plate-layer appeared in no wise unwilling to postpone for a few moments his tiring and chilly underground patrol; he put down his pick before answering.

"Well, that's not surprising, is it? People who are rich enough to travel first-class always come by the express which gets to Brives at 2.50 a.m."

"I see," said FranÇois Paul; "that's reasonable: and more practical for travellers to Brives or Cahors. But what about the people who want to get out at Gourdon, or Souillac, or VerriÈres, or any of the small stations where the express doesn't stop?"

"I don't know," said the plate-layer; "but I suppose they have to get out at Brives or Cahors and drive, or else travel by the day trains, which are fast to Brives and slow afterwards."

FranÇois Paul did not press the matter. He lit a pipe and breathed upon his benumbed fingers.

"Hard times, these, and no mistake!"

The plate-layer seemed sorry for him.

"I don't suppose you're an independent gentleman, but why don't you try to get taken on here?" he suggested. "They want hands here."

"Oh, do they?"

"That's the fact; this is the foreman coming along now: would you like me to speak to him for you?"

"No hurry," replied FranÇois Paul. "'Course, I'm not saying no, but I should like to see what sort of work it is they're doing here: it might not suit me; I shall still have time to get a couple of words with him," and with his eyes on the ground the tramp slowly walked along the embankment away from the plate-layer.

The foreman met and passed him, and came up to the plate-layer at the mouth of the tunnel.

"Well, Michu, how goes it with you? Still got the old complaint?"

"Middling, boss," the worthy fellow answered: "just keeping up, you know. And how's yourself? And the work? When shall you finish? I don't know if you know it, but these trains stopping regularly in my section give me an extra lot of work."

"How's that?" the foreman enquired in surprise.

"The engine drivers take advantage of the stop to empty their ash-pans, and they leave a great heap of mess there in my tunnel, which I'm obliged to clear away. In the ordinary way they dump it somewhere else: where, I don't know, but not in my tunnel, and that's all I care about."

The foreman laughed.

"You're a good 'un, Michu! If I were you I would ask the Company to give me another man or two."

"And do you suppose the Company would?" Michu retorted. "By the way, that poor devil who is going along there, shivering with cold and hunger, was grumbling to me just now, and I advised him to ask you to take him on. What do you think he said? Why, that he would have a look at the work first, and off he went."

"It's a fact, Michu, that it's mighty difficult to come across people who mean business nowadays. It's quite true that I want more hands. But if that chap doesn't ask me to engage him in another minute, I'll kick him out. The embankment is not public property, and I don't trust these rascals who are for ever coming and going among the workmen to see what mischief they can make. I'll go and cast an eye over the bolts and things, for there are all sorts of vagrants about the neighbourhood just now."

"And criminals, too," said old Michu. "I suppose you have heard of the murder up at the chÂteau of Beaulieu?"

"Rather! My men are talking of nothing else. But you are right, Michu, I will get a closer look at all strangers, and at your friend in particular."

The foreman stopped abruptly; he had been examining the foot of the embankment, and was standing quite still, watching. The plate-layer followed his glance, and also stood fixed. After a few moments' silence the two men looked at each other and smiled. In the half-light of the valley they had seen the outline of a gendarme; he was on foot and appeared to be looking for somebody, while making no attempt to remain unseen himself.

"Good!" whispered Michu; "that's sergeant Doucet: I know him by his stripes. They say the murder was not committed by anyone belonging to this part of the country; everybody was fond of the Marquise de Langrune."

"Look! Look!" the foreman broke in, pointing to the gendarme who was slowly climbing up the embankment. "It looks as if the sergeant were making for the gentleman who was looking for work just now and hoped he would not find it. The sergeant's got a word for him, eh, what?"

"That might be," said Michu after a moment's further watching. "That chap has a villainous, ugly face. One can tell from the way he's dressed that he don't belong to our parts."

The two men waited with utmost interest to see what was going to happen.

Sergeant Doucet reached the top of the embankment at last and hurried past the navvies, who stopped their work to stare inquisitively after the representative of authority. Fifty yards beyond them, FranÇois Paul, wrapped in thought, was walking slowly down towards the station of VerriÈres. Hearing the sound of steps behind him, he turned. When he saw the sergeant he frowned. He glanced rapidly about him and saw that while he was alone with the gendarme, so that no one could overhear what they said, however loudly they might speak, they were yet in such a position that every sign and movement they made would be perfectly visible to whoever might watch them. And as the gendarme paused a few paces from him and—remarkable fact—seemed to be on the point of bringing his hand to his cap in salute, the mysterious tramp rapped out:

"I thought I said no one was to disturb me, sergeant?"

The sergeant took a pace forward.

"I beg your pardon, Inspector, but I have important news for you."

For this FranÇois Paul, whom the sergeant thus respectfully addressed as Inspector, was no other than an officer of the secret police who had been sent down to Beaulieu the day before from head-quarters in Paris.

He was no ordinary officer. As if M. Havard had had an idea that the Langrune affair would prove to be puzzling and complicated, he had singled out the very best of his detectives, the most expert inspector of them all—Juve. It was Juve who for the last forty-eight hours had been prowling about the chÂteau of Beaulieu disguised as a tramp, and had had himself arrested with Bouzille that he might prosecute his own investigations without raising the slightest suspicion as to his real identity.

Juve made a face expressive of his vexation at the over-deferential attitude of the sergeant.

"Do pay attention!" he said low. "We are being watched. If I must go back with you, pretend to arrest me. Slip the handcuffs on me!"

"I beg your pardon, Inspector: I don't like to," the gendarme answered.

For all reply, Juve turned his back on him.

"Look here," he said, "I will take a step or two forward as if I meant to run away; then you must put your hand on my shoulder roughly, and I will stumble; when I do, slip the bracelets on."

From the mouth of the tunnel the plate-layer, the foreman and the navvies all followed with their eyes the unintelligible conversation passing between the gendarme and the tramp a hundred yards away. Suddenly they saw the man try to get off and the sergeant seize him almost simultaneously. A few minutes later the individual, with his hands linked together in front of him, was obediently descending the steep slope of the embankment, by the gendarme's side, and then the two men disappeared behind a clump of trees.

"I understand why that chap was not very keen on getting taken on here," said the foreman. "His conscience was none too easy!"

As they walked briskly in the direction of Beaulieu Juve asked the sergeant:

"What has happened at the chÂteau, then?"

"They know who the murderer is, Inspector," the sergeant answered. "Little Mlle. ThÉrÈse——"