Two days later Inspector Willis sat once again in the office of M. Max, the head of the French Excise Department in Paris. The Frenchman greeted him politely, but without enthusiasm.

“Ah, monsieur,” he said, “you have not received my letter? No? I wrote to your department yesterday.”

“It hadn't come, sir, when I left,” Willis returned. “But perhaps if it is something I should know, you could tell me the contents?”

“But certainly, monsieur. It is easily done. A thousand regrets, but I fear my department will not be of much service to you.”

“No, sir?” Willis looked his question.

“I fear not. But I shall explain,” M. Max gesticulated as he talked. “After your last visit here I send two of my men to Bordeaux. They make examination, but at first they see nothing suspicious. When the Girondin comes in they determine to test your idea of the brandy loading. They go in a boat to the wharf at night. They pull in between the rows of piles. They find the spaces between the tree trunks which you have described. They know there must be a cellar behind. They hide close by; they see the porthole lighted up; they watch the pipe go in, all exactly as you have said. There can be no doubt brandy is secretly loaded at the Lesque.”

“It seemed the likely thing, sir,” Willis commented.

“Ah, but it was good to think of. I wish to congratulate you on finding it out.” M. Max made a little bow. “But to continue. My men wonder how the brandy reaches the sawmill. Soon they think that the lorries must bring it. They think so for two reasons. First, they can find no other way. The lorries are the only vehicles which approach; nothing goes by water; there cannot be a tunnel, because there is no place for the other end. There remains only the lorries. Second, they think it is the lorries because the drivers change the numbers. It is suspicious, is it not? Yes? You understand me?”

“Perfectly, sir.”

“Good. My men then watch the lorries. They get help from the police at Bordeaux. They find the firewood trade is a nothing.” M. Max shrugged his shoulders. “There are five firms to which the lorries go, and of the five, four—” His gesture indicated a despair too deep for words. “To serve them, it is but a blind; so my men think. But the fifth firm, it is that of Raymond Fils, one of the biggest distilleries of Bordeaux. That Raymond Fils are sending out the brandy suggests itself to my men. At last the affair marches.”

M. Max paused, and Willis bowed to signify his appreciation of the point.

“My men visit Raymond Fils. They search into everything. They find the law is not broken. All is in order. They are satisfied.”

“But, sir, if these people are smuggling brandy into England—” Willis was beginning when the other interrupted him.

“But yes, monsieur, I grasp your point. I speak of French law; it is different from yours. Here duty is not charged on just so much spirit as is distilled. We grant the distiller a license, and it allows him to distill any quantity up to the figure the license bears. But, monsieur, Raymond Fils are—how do you say it?—well within their limit? Yes? They do not break the French law.”

“Therefore, sir, you mean you cannot help further?”

“My dear monsieur, what would you? I have done my best for you. I make inquiries. The matter is not for me. With the most excellent wish to assist, what more can I?”

Willis, realizing he could get no more, rose.

“Nothing, sir, except to accept on my own part and that of my department our hearty thanks for what you have done. I can assure you, sir, I quite understand your position, and I greatly appreciate your kindness.”

M. Max also had risen. He politely repeated his regrets, and with mutual compliments the two men parted.

Willis had once spent a holiday in Paris, and he was slightly acquainted with the city. He strolled on through the busy streets, brilliant in the pale autumn sunlight, until he reached the Grands Boulevards. There entering a cafe, he sat down, called for a bock, and settled himself to consider his next step.

The position created by M. Max's action was disconcerting. Willis felt himself stranded, literally a stranger in a strange land, sent to carry out an investigation among a people whose language he could not even speak! He saw at once that his task was impossible. He must have local help or he could proceed no further.

He thought of his own department. The Excise had failed him. What about the Surete?

But a very little thought convinced him that he was even less likely to obtain help from this quarter. He could only base an appeal on the possibility of a future charge of conspiracy to murder, and he realized that the evidence for that was too slight to put forward seriously.

What was to be done? So far as he could see, but one thing. He must employ a private detective. This plan would meet the language difficulty by which he was so completely hung up.

He went to a call office and got his chief at the Yard on the long distance wire. The latter approved his SUGGESTION, and recommended M. Jules Laroche of the Rue du Sommerard near the Sorbonne. Half an hour later Willis reached the house.

M. Laroche proved to be a tall, unobtrusive-looking man of some five-and-forty, who had lived in London for some years and spoke as good English as Willis himself. He listened quietly and without much apparent interest to what his visitor had to tell him, then said he would be glad to take on the job.

“We had better go to Bordeaux this evening, so as to start fresh tomorrow,” Willis suggested.

“Two o'clock at the d'Orsay station,” the other returned. “We have just time. We can settle our plans in the train.”

They reached the St Jean station at Bordeaux at 10.35 that night, and drove to the Hotel d'Espagne. They had decided that they could do nothing until the following evening, when they would go out to the clearing and see what a search of the mill premises might reveal.

Next morning Laroche vanished, saying he had friends in the town whom he wished to look up, and it was close on dinner-time before he put in an appearance.

“I have got some information that may help,” he said, as Willis greeted him. “Though I'm not connected with the official force, we are very good friends and have worked into each other's hands. I happen to know one of the officers of the local police, and he got me the information. It seems that a M. Pierre Raymond is practically the owner of Raymond Fils, the distillers you mentioned. He is a man of about thirty, and the son of one of the original brothers. He was at one time comfortably off, and lived in a pleasant villa in the suburbs. But latterly he has been going the pace, and within the last two years he let his villa and bought a tiny house next door to the distillery, where he is now living. It is believed his money went at Monte Carlo, indeed it seems he is a wrong 'un all round. At all events he is known to be hard up now.”

“And you think he moved in so that he could load up that brandy at night?”

“That's what I think,” Laroche admitted. “You see, there is the motive for it as well. He wouldn't join the syndicate unless he was in difficulties. I fancy M. Pierre Raymond will be an INTERESTING study.”

Willis nodded. The SUGGESTION was worth investigation, and he congratulated himself on getting hold of so excellent a colleague as this Laroche seemed to be.

The Frenchman during the day had hired a motor bicycle and sidecar, and as dusk began to fall the two men left their hotel and ran out along the Bayonne road until they reached the Lesque. There they hid their vehicle behind some shrubs, and reaching the end of the lane, turned down it.

It was pitch dark among the trees, and they had some difficulty in keeping the track until they reached the clearing. There a quarter moon rendered objects dimly visible, and Willis at once recognized his surroundings from the description he had received from Hilliard and Merriman.

“You see, somebody is in the manager's house,” he whispered, pointing to a light which gleamed in the window. “If Henri has taken over Coburn's job he may go down to the mill as Coburn did. Hadn't we better wait and see?”

The Frenchman agreeing, they moved round the fringe of trees at the edge of the clearing, just as Merriman had done on a similar occasion some seven weeks earlier, and as they crouched in the shelter of a clump of bushes in front of the house, they might have been interested to know that it was from these same shrubs that that disconsolate sentimentalist had lain dreaming of his lady love, and from which he had witnessed her father's stealthy journey to the mill.

It was a good deal colder tonight than on that earlier occasion when watch was kept on the lonely house. The two men shivered as they drew their collars higher round their necks, and crouched down to get shelter from the bitter wind. They had resigned themselves to a weary vigil, during which they dared not even smoke.

But they had not to wait so long after all. About ten the light went out in the window and not five minutes later they saw a man appear at the side door and walk towards the mill. They could not see his features, though Willis assumed he was Henri. Twenty minutes later they watched him return, and then all once more was still.

“We had better give him an hour to get to bed,” Willis whispered. “If he were to look out it wouldn't do for him to see two detectives roaming about his beloved clearing.”

“We might go at eleven,” Laroche proposed, and so they did.

Keeping as much as possible in the shelter of the bushes, they approached the mill. Willis had got a sketch-plan of the building from Merriman, and he moved round to the office door. His bent wire proved as efficacious with French locks as with English, and in a few moments they stood within, with the door shut behind them.

“Now,” said Willis, carefully shading the beam of his electric torch, “let's see those lorries first of all.”

As has already been stated, the garage was next to the office, and passing through the communicating door, the two men found five of the ponderous vehicles therein. A moment's examination of the number plates showed that on all the machines the figures were separate from the remainder of the lettering, being carried on small brass plates which dropped vertically into place through slots in the main castings. But the joint at each side of the number was not conspicuous because similar vertical lines were cut into the brass between each letter of the whole legend.

“That's good,” Laroche observed. “Make a thing unnoticeable by multiplying it!”

Of the five lorries, two were loaded with firewood and three empty. The men moved round examining them with their torches.

“Hallo,” Laroche called suddenly in a low voice, “what have we here, Willis?”

The inspector crossed over to the other, who was pointing to the granolithic floor in front of him. One of the empty lorries was close to the office wall, and the Frenchman stood between the two. On the floor were three drops of some liquid.

“Can you smell them?” he inquired.

Willis knelt down and sniffed, then slowly got up again.

“Good man,” he said, with a trace of excitement in his manner. “It's brandy right enough.”

“Yes,” returned the other. “Security has made our nocturnal friend careless. The stuff must have come from this lorry, I fancy.”

They turned to the vehicle and examined it eagerly. For some time they could see nothing remarkable, but presently it gave up its secret The deck was double! Beneath it was a hollow space some six feet by nine long, and not less than three inches deep. And not only so. This hollow space was continued up under the unusually large and wide driver's seat, save for a tiny receptacle for petrol. In a word the whole top of the machine was a vast secret tank.

The men began measuring and calculating, and they soon found that no less than one hundred and fifty gallons of liquid could be carried therein.

“One hundred and fifty gallons of brandy per trip!” Willis ejaculated. “Lord! It's no wonder they make it pay.”

They next tackled the problem of how the tank was filled and emptied, and at last their perseverance was rewarded. Behind the left trailing wheel, under the framing, was a small hinged door about six inches square and fastened by a spring operated by a mock rivet head. This being opened, revealed a cavity containing a pipe connected to the tank and fitted with a stop-cock and the half of a union coupling.

“The pipe which connects with that can't be far away,” Laroche suggested. “We might have a look round for it.”

The obvious place was the wall of the office, which ran not more than three feet from the vehicle. It was finished with vertical tongued and V-jointed sheeting, and a comparatively short search revealed the loose board the detectives were by this time expecting. Behind it was concealed a pipe, jointed concertina-wise, and ending in the other half of the union coupling. It was evident the joints would allow the half coupling to be pulled out and connected with that on the lorry. The pipe ran down through the floor, showing that the lorry could be emptied by gravity.

“A good safe scheme,” Laroche commented. “If I had seen that lorry a hundred times I should never have suspected a tank. It's well designed.”

They turned to examine the other vehicles. All four were identical in appearance with the first, but all were strictly what they seemed, containing no secret receptacle.

“Merriman said they had six lorries,” Willis remarked. “I wonder where the sixth is.”

“At the distillery, don't you think?” the Frenchman returned. “Those drops prove that manager fellow has just been unloading this one. I expect he does it every night. But if so, Raymond must load a vehicle every night too.”

“That's true. We may assume the job is done every night, because Merriman watched Coburn come down here three nights running. It was certainly to unload the lorry.”

“Doubtless; and he probably came at two in the morning on account of his daughter.”

“That means there are two tank lorries,” Willis went on, continuing his own line of thought. “I say, Laroche, let's mark this one so that we may know it again.”

They made tiny scratches on the paint at each corner of the big vehicle, then Willis turned back to the office.

“I'd like to find that cellar while we're here,” he remarked. “We know there is a cellar, for those Customs men saw the Girondin loaded from it. We might have a look round for the entrance.”

Then ensued a search similar to that which Willis had carried out in the depot at Ferriby, except that in this case they found what they were looking for in a much shorter time. In the office was a flat roll-topped desk, with the usual set of drawers at each side of the central knee well, and when Willis found it was clamped to the floor he felt he need go no further. On the ground in the knee well, and projecting out towards the revolving chair in front, was a mat. Willis raised it, and at once observed a joint across the boards where in ordinary circumstances no joint should be. He fumbled and pressed and pulled, and in a couple of minutes he had the satisfaction of seeing the floor under the well rise and reveal the head of a ladder leading down into the darkness below.

“Here we are,” he called softly to Laroche, who was searching at the other side of the room.

The cellar into which the two detectives descended was lined with timber like that at Ferriby. Indeed the two were identical, except that only one passage—that under the wharf—led out of this one. It contained a similar large tun with a pipe leading down the passage under the wharf, on which was a pump. The only difference was in the connection of the pipes. At Ferriby the pump conveyed from the wharf to the tun, here it was from the tun to the wharf. The pipe from the garage came down through the ceiling and ran direct into the tun.

The two men walked down the passage towards the river. Here also the arrangement was the same as at Ferriby, and they remained only long enough for Willis to point out to the Frenchman how the loading apparatus was worked.

“Well,” said the former, as they returned to the office, “that's not so bad for one day. I suppose it's all we can do here. If we can learn as much at that distillery we shall soon have all we want.”

Laroche pointed to a chair.

“Sit down a moment,” he invited. “I have been thinking over that plan we discussed in the train, of searching the distillery at night, and I don't like it. There are too many people about, and we are nearly certain to be seen. It's quite different from working a place like this.”

“Quite,” Willis answered rather testily. “I don't like it either, but what can we do?”

“I'll tell you what I should do.” Laroche leaned forward and checked his points on his fingers. “That lorry had just been unloaded. It's empty now, and if our theory is correct it will be taken to the distillery tomorrow and left there over-night to be filled up again. Isn't that so?”

Willis nodded impatiently and the other went on:

“Now, it is clear that no one can fill up that tank without leaving finger-prints on the pipe connections in that secret box. Suppose we clean those surfaces now, and suppose we come back here the night after tomorrow, before the man here unloads, we could get the prints of the person who filled up in the distillery.”

“Well,” Willis asked sharply, “and how would that help us?”

“This way. Tomorrow you will be an English distiller with a forest you could get cheap near your works. You have an idea of running your stills on wood fires. You naturally call to see how M. Raymond does it, and you get shown over his works. You have prepared a plan of your proposals. You hand it to him when he can't put it down on a desk. He holds it between his fingers and thumb, and eventually returns it to you. You go home and use powder. You have his finger-prints. You compare the two sets.”

Willis was impressed. The plan was simple, and it promised to gain for them all the information they required without recourse to a hazardous nocturnal visit to the distillery. But he wished he had thought of it himself.

“We might try it,” he admitted, without enthusiasm. “It couldn't do much harm anyway.”

They returned to the garage, opened the secret lid beneath the lorry, and with a cloth moistened with petrol cleaned the fittings. Then after a look round to make sure that nothing had been disturbed, they let themselves out of the shed, regained the lane and their machine, and some forty minutes later were in Bordeaux.

On reconsideration they decided that as Raymond might have obtained Willis's description from Captain Beamish, it would be wiser for Laroche to visit the distillery. Next morning, therefore, the latter bought a small writing block, and taking an inside leaf, which he carefully avoided touching with his hands, he drew a cross-section of a wood-burning fire-box copied from an illustration in a book of reference in the city library, at the same time reading up the subject so as to be able to talk on it without giving himself away. Then he set out on his mission.

In a couple of hours he returned.

“Got that all right,” he exclaimed, as he rejoined the inspector. “I went and saw the fellow; said I was going to start a distillery in the Ardennes where there was plenty of wood, and wanted to see his plant. He was very civil, and took me round and showed me everything. There is a shed there above the still furnaces with hoppers for the firewood to go down, and in it was standing the lorry—the lorry, I saw our marks on the corner. It was loaded with firewood, and he explained that it would be emptied last thing before the day-shift left, so as to do the stills during the night. Well, I got a general look round the concern, and I found that the large tuns which contain the finished brandy were just at the back of the wall of the shed where the lorry was standing. So it is easy to see what happens. Evidently there is a pipe through the wall, and Raymond comes down at night and fills up the lorry.”

“And did you get his finger-prints?”

“Have 'em here.”

Locking the door of their private room, Laroche took from his pocket the sketch he had made.

“He held this up quite satisfactorily,” he went on, “and there should be good prints.”

Willis had meanwhile spread a newspaper on the table and taken from his suitcase a small bottle of powdered lamp-black and a camel's-hair brush. Laying the sketch on the newspaper he gently brushed some of the black powder over it, blowing off the surplus. To the satisfaction of both men, there showed up near the left bottom corner the distinct mark of a left thumb.

“Now the other side.”

Willis turned the paper and repeated the operation on the back. There he got prints of a left fore and second finger.

“Excellent, clear prints, those,” Willis commented, continuing: “And now I have something to tell you. While you were away I have been thinking over this thing, and I believe I've got an idea.”

Laroche looked interested, and the other went on slowly:

“There are two brandy-carrying lorries. Every night one of these lies at the distillery and the other at the clearing; one is being loaded and the other unloaded; and every day the two change places. Now we may take it that neither of those lorries is sent to any other place in the town, lest the brandy tanks might be discovered. For the same reason, they probably only make the one run mentioned per day. Is that right so far?”

“I should think so,” Laroche replied cautiously.

“Very well. Let us suppose these two lorries are Nos. 1 and 2. No. 1 goes to the distillery say every Monday, Wednesday and Friday, and returns on the other three days, while No. 2 does vice versa, one trip each day remember. And this goes on day after day, week after week, month after month. Now is it too much to assume that sooner or later someone is bound to notice this—some worker at the clearing or the distillery, some policeman on his beat, some clerk at a window over-looking the route? And if anyone notices it will he not wonder why it always happens that these two lorries go to this one place and to no other, while the syndicate has six lorries altogether trading into the town? And if this observer should mention his discovery to someone who could put two and two together, suspicion might be aroused, investigation undertaken, and presently the syndicate is up a tree. Now do you see what I'm getting at?”

Laroche had been listening eagerly, and now he made a sudden gesture.

“But of course!” he cried delightedly. “The changing of the numbers!”

“The changing of the numbers,” Willis repeated. “At least, it looks like that to me. No. 1 does the Monday run to the distillery. They change the number plate, and No. 4 does it on Wednesday, while No. 1 runs to some other establishment, where it can be freely examined by anyone who is interested. How does it strike you?”

“You have got it. You have certainly got it.” Laroche was more enthusiastic than the inspector had before seen him. “It's what you call a cute scheme, quite on par with the rest of the business. They didn't leave much to chance, these! And yet it was this very precaution that gave them away.”

“No doubt, but that was an accident.”

“You can't,” said the Frenchman sententiously, “make anything completely watertight.”

The next night they went out to the clearing, and as soon as it was dark once more entered the shed. There with more powder—white this time-they tested the tank lorry for finger-marks. As they had hoped, there were several on the secret fittings, among others a clear print of a left thumb on the rivet head of the spring.

A moment's examination only was necessary. The prints were those of M. Pierre Raymond.

Once again Inspector Willis felt that he ought to have completed his case, and once again second thoughts showed him that he was as far away from that desired end as ever. He had been trying to find accomplices in the murder of Coburn, and by a curious perversity, instead of finding them he had bit by bit solved the mystery of the Pit-Prop Syndicate. He had shown, firstly, that they were smuggling brandy, and, secondly, how they were doing it. For that he would no doubt get a reward, but such was not his aim. What he wanted was to complete his own case and get the approval of his own superiors and bring promotion nearer. And in this he had failed.

For hours he pondered over the problem, then suddenly an idea which seemed promising flashed into his mind. He thought it over with the utmost care, and finally decided that in the absence of something better he must try it.

In the morning the two men travelled to Paris, and Willis, there taking leave of his colleague, crossed to London, and an hour later was with his chief at the Yard.