Dupre sat at one of the round tables in the Cafe Vernon, with a glass of absinthe before him, which he sipped every now and again. He looked through the open door, out to the Boulevard, and saw passing back and forth with the regularity of a pendulum, a uniformed policeman. Dupre laughed silently as he noticed this evidence of law and order. The Cafe Vernon was under the protection of the Government. The class to which Dupre belonged had sworn that it would blow the cafe into the next world, therefore the military-looking policeman walked to and fro on the pavement to prevent this being done, so that all honest citizens might see that the Government protects its own. People were arrested now and then for lingering around the cafe: they were innocent, of course, and by-and-by the Government found that out and let them go. The real criminal seldom acts suspiciously. Most of the arrested persons were merely attracted by curiosity. "There," said one to another, "the notorious Hertzog was arrested."

The real criminal goes quietly into the cafe, and orders his absinthe, as Dupre had done. And the policeman marches up and down keeping an eye on the guiltless. So runs the world.

There were few customers in the cafe, for people feared the vengeance of Hertzog's friends. They expected some fine day that the cafe would be blown to atoms, and they preferred to be taking their coffee and cognac somewhere else when that time came. It was evident that M. Sonne, the proprietor of the cafe, had done a poor stroke of business for himself when he gave information to the police regarding the whereabouts of Hertzog, notwithstanding the fact that his cafe became suddenly the most noted one in the city, and that it now enjoyed the protection of the Government.

Dupre seldom looked at the proprietor, who sat at the desk, nor at the waiter, who had helped the week before to overpower Hertzog. He seemed more intent on watching the minion of the law who paced back and forth in front of the door, although he once glanced at the other minion who sat almost out of sight at the back of the cafe, scrutinising all who came in, especially those who had parcels of any kind. The cafe was well guarded, and M. Sonne, at the desk, appeared to be satisfied with the protection he was receiving.

When customers did come in they seldom sat at the round metal tables, but went direct to the zinc-covered bar, ordered their fluid and drank it standing, seeming in a hurry to get away. They nodded to M. Sonne and were evidently old frequenters of the cafe who did not wish him to think they had deserted him in this crisis, nevertheless they all had engagements that made prompt departure necessary. Dupre smiled grimly when he noticed this. He was the only man sitting at a table. He had no fears of being blown up. He knew that his comrades were more given to big talk than to action. He had not attended the last meeting, for he more than suspected the police had agents among them; besides, his friend and leader, Hertzog, had never attended meetings. That was why the police had had such difficulty in finding him. Hertzog had been a man of deeds not words. He had said to Dupre once, that a single determined man who kept his mouth shut, could do more against society than all the secret associations ever formed, and his own lurid career had proved the truth of this. But now he was in prison, and it was the treachery of M. Sonne that had sent him there. As he thought of this, Dupre cast a glance at the proprietor and gritted his teeth.

The policeman at the back of the hall, feeling lonely perhaps, walked to the door and nodded to his parading comrade. The other paused for a moment on his beat, and they spoke to each other. As the policeman returned to his place, Dupre said to him--

"Have a sip with me."

"Not while on duty," replied the officer with a wink.

"Garcon," said Dupre quietly, "bring me a caraffe of brandy. Fin champagne."

The garcon placed the little marked decanter on the table with two glasses. Dupre filled them both. The policeman, with a rapid glance over his shoulder, tossed one off, and smacked his lips. Dupre slowly sipped the other while he asked--

"Do you anticipate any trouble here?"

"Not in the least," answered the officer confidently. "Talk, that's all."

"I thought so," said Dupre.

"They had a meeting the other night--a secret meeting;" the policeman smiled a little as he said this. "They talked a good deal. They are going to do wonderful things. A man was detailed to carry out this job."

"And have you arrested him?" questioned Dupre.

"Oh dear, no. We watch him merely. He is the most frightened man in the city to-night. We expect him to come and tell us all about it, but we hope he won't. We know more about it than he does."

"I dare say; still it must have hurt M. Sonne's business a good deal."

"It has killed it for the present. People are such cowards. But the Government will make it all right with him out of the secret fund. He won't lose anything."

"Does he own the whole house, or only the cafe?"

"The whole house. He lets the upper rooms, but nearly all the tenants have left. Yet I call it the safest place in the city. They are all poltroons, the dynamiters, and they are certain to strike at some place not so well guarded. They are all well known to us, and the moment one is caught prowling about here he will be arrested. They are too cowardly to risk their liberty by coming near this place. It's a different thing from leaving a tin can and fuse in some dark corner when nobody is looking. Any fool can do that."

"Then you think this would be a good time to take a room here? I am looking for one in this neighbourhood," said Dupre.

"You couldn't do better than arrange with M. Sonne. You could make a good bargain with him now, and you would be perfectly safe."

"I am glad that you mentioned it; I will speak to M. Sonne to-night, and see the rooms to-morrow. Have another sip of brandy?"

"No, thank you, I must be getting back to my place. Just tell M. Sonne, if you take a room, that I spoke to you about it."

"I will. Good-night."

Dupre paid his bill and tipped the garcon liberally. The proprietor was glad to hear of any one wanting rooms. It showed the tide was turning, and an appointment was made for next day.

Dupre kept his appointment, and the concierge showed him over the house. The back rooms were too dark, the windows being but a few feet from the opposite wall. The lower front rooms were too noisy. Dupre said that he liked quiet, being a student. A front room on the third floor, however, pleased him, and he took it. He well knew the necessity of being on good terms with the concierge, who would spy on him anyhow, so he paid just a trifle more than requisite to that functionary, but not enough to arouse suspicion. Too much is as bad as too little, a fact that Dupre was well aware of.

He had taken pains to see that his window was directly over the front door of the cafe, but now that he was alone and the door locked, he scrutinised the position more closely. There was an awning over the front of the cafe that shut off his view of the pavement and the policeman marching below. That complicated matters. Still he remembered that when the sun went down the awning was rolled up. His first idea when he took the room was to drop the dynamite from the third story window to the pavement below, but the more he thought of that plan the less he liked it. It was the sort of thing any fool could do, as the policeman had said. It would take some thinking over. Besides, dynamite dropped on the pavement would, at most, but blow in the front of the shop, kill the perambulating policeman perhaps, or some innocent passer-by, but it would not hurt old Sonne nor yet the garcon who had made himself so active in arresting Hertzog.

Dupre was a methodical man. He spoke quite truly when he said he was a student. He now turned his student training on the case as if it were a problem in mathematics.

First, the dynamite must be exploded inside the cafe. Second, the thing must be done so deftly that no suspicion could fall on the perpetrator. Third, revenge was no revenge when it (A) killed the man who fired the mine, or (B) left a trail that would lead to his arrest.

Dupre sat down at his table, thrust his hands in his pockets, stretched out his legs, knit his brows, and set himself to solve the conundrum. He could easily take a handbag filled with explosive material into the cafe. He was known there, but not as a friend of Hertzog's. He was a customer and a tenant, therefore doubly safe. But he could not leave the bag there, and if he stayed with it his revenge would rebound on himself. He could hand the bag to the waiter saying he would call for it again, but the waiter would naturally wonder why he did not give it to the concierge, and have it sent to his rooms; besides, the garcon was wildly suspicious. The waiter felt his unfortunate position. He dare not leave the Cafe Vernon, for he now knew that he was a marked man. At the Vernon he had police protection, while if he went anywhere else he would have no more safeguard than any other citizen; so he stayed on at the Vernon, such a course being, he thought, the least of two evils. But he watched every incomer much more sharply than did the policeman.

Dupre also realised that there was another difficulty about the handbag scheme. The dynamite must be set off either by a fuse or by clockwork machinery. A fuse caused smoke, and the moment a man touched a bag containing clockwork his hand felt the thrill of moving machinery. A man who hears for the first time the buzz of the rattlesnake's signal, like the shaking of dry peas in a pod, springs instinctively aside, even though he knows nothing of snakes. How much more, therefore, would a suspicious waiter, whose nerves were all alert for the soft, deadly purr of dynamite mechanism, spoil everything the moment his hand touched the bag? Yes, Dupre reluctantly admitted to himself, the handbag theory was not practical. It led to either self-destruction or prison.

What then was the next thing, as fuse or mechanism were unavailable? There was the bomb that exploded when it struck, and Dupre had himself made several. A man might stand in the middle of the street and shy it in through the open door. But then he might miss the doorway. Also until the hour the cafe closed the street was as light as day. Then the policeman was all alert for people in the middle of the street. His own safety depended upon it too. How was the man in the street to be dispensed with, yet the result attained? If the Boulevard was not so wide, a person on the opposite side in a front room might fire a dynamite bomb across, as they do from dynamite guns, but then there was--

"By God!" cried Dupre, "I have it!"

He drew in his outstretched legs, went to the window and threw it open, gazing down for a moment at the pavement below. He must measure the distance at night--and late at night too--he said to himself. He bought a ball of cord, as nearly the colour of the front of the building as possible. He left his window open, and after midnight ran the cord out till he estimated that it about reached the top of the cafe door. He stole quietly down and let himself out, leaving the door unlatched. The door to the apartments was at the extreme edge of the building, while the cafe doors were in the middle, with large windows on each side. As he came round to the front, his heart almost ceased to beat when a voice from the cafe door said--

"What do you want? What are you doing here at this hour?"

The policeman had become so much a part of the pavement in Dupre's mind that he had actually forgotten the officer was there night and day. Dupre allowed himself the luxury of one silent gasp, then his heart took up its work again.

"I was looking for you," he said quietly. By straining his eyes he noticed at the same moment that the cord dangled about a foot above the policeman's head, as he stood in the dark doorway.

"I was looking for you. I suppose you don't know of any--any chemist's shop open so late as this? I have a raging toothache and can't sleep, and I want to get something for it."

"Oh, the chemist's at the corner is open all night. Ring the bell at the right hand."

"I hate to disturb them for such a trifle."

"That's what they're there for," said the officer philosophically.

"Would you mind standing at the other door till I get back? I'll be as quick as I can. I don't wish to leave it open unprotected, and I don't want to close it, for the concierge knows I'm in and he is afraid to open it when any one rings late. You know me, of course; I'm in No. 16."

"Yes, I recognise you now, though I didn't at first. I will stand by the door until you return."

Dupre went to the corner shop and bought a bottle of toothache drops from the sleepy youth behind the counter. He roused him up however, and made him explain how the remedy was to be applied. He thanked the policeman, closed the door, and went up to his room. A second later the cord was cut at the window and quietly pulled in.

Dupre sat down and breathed hard for a few moments.

"You fool!" he said to himself; "a mistake or two like that and you are doomed. That's what comes of thinking too much on one branch of your subject. Another two feet and the string would have been down on his nose. I am certain he did not see it; I could hardly see it myself, looking for it. The guarding of the side door was an inspiration. But I must think well over every phase of the subject before acting again. This is a lesson."

As he went on with his preparations it astonished him to find how many various things had to be thought of in connexion with an apparently simple scheme, the neglect of any one of which would endanger the whole enterprise. His plan was a most uncomplicated one. All he had to do was to tie a canister of dynamite at the end of a string of suitable length, and at night, before the cafe doors were closed, fling it from his window so that the package would sweep in by the open door, strike against the ceiling of the cafe, and explode. First he thought of holding the end of the cord in his hand at the open window, but reflection showed him that if, in the natural excitement of the moment, he drew back or leant too far forward the package might strike the front of the house above the door, or perhaps hit the pavement. He therefore drove a stout nail in the window-sill and attached the end of the cord to that. Again, he had to render his canister of explosive so sensitive to any shock that he realised if he tied the cord around it and flung it out into the night the can might go off when the string was jerked tight and the explosion take place in mid-air above the street. So he arranged a spiral spring between can and cord to take up harmlessly the shock caused by the momentum of the package when the string became suddenly taut. He saw that the weak part of his project was the fact that everything would depend on his own nerve and accuracy of aim at the critical moment, and that a slight miscalculation to the right or to the left would cause the bomb, when falling down and in, to miss the door altogether. He would have but one chance, and there was no opportunity of practising. However, Dupre, who was a philosophical man, said to himself that if people allowed small technical difficulties to trouble them too much, nothing really worth doing would be accomplished in this world. He felt sure he was going to make some little mistake that would ruin all his plans, but he resolved to do the best he could and accept the consequences with all the composure at his command.

As he stood by the window on the fatal night with the canister in his hand he tried to recollect if there was anything left undone or any tracks remaining uncovered. There was no light in his room, but a fire burned in the grate, throwing flickering reflections on the opposite wall.

"There are four things I must do," he murmured: "first, pull up the string; second, throw it in the fire; third, draw out the nail; fourth, close the window."

He was pleased to notice that his heart was not beating faster than usual. "I think I have myself well in hand, yet I must not be too cool when I get downstairs. There are so many things to think of all at one time," he said to himself with a sigh. He looked up and down the street. The pavement was clear. He waited until the policeman had passed the door. He would take ten steps before he turned on his beat. When his back was towards the cafe door Dupre launched his bomb out into the night.

He drew back instantly and watched the nail. It held when the jerk came. A moment later the whole building lurched like a drunken man, heaving its shoulders as it were. Dupre was startled by a great square of plaster coming down on his table with a crash. Below, there was a roar of muffled thunder. The floor trembled under him after the heave. The glass in the window clattered down, and he felt the air smite him on the breast as if some one had struck him a blow.

He looked out for a moment. The concussion had extinguished the street lamps opposite. All was dark in front of the cafe where a moment before the Boulevard was flooded with light. A cloud of smoke was rolling out from the lower part of the house.

"Four things," said Dupre, as he rapidly pulled in the cord. It was shrivelled at the end. Dupre did the other three things quickly.

Everything was strangely silent, although the deadened roar of the explosion still sounded dully in his ears. His boots crunched on the plaster as he walked across the room and groped for the door. He had some trouble in pulling it open. It stuck so fast that he thought it was locked; then he remembered with a cold shiver of fear that the door had been unlocked all the time he had stood at the window with the canister in his hand.

"I have certainly done some careless thing like that which will betray me yet; I wonder what it is?"

He wrenched the door open at last. The lights in the hall were out; he struck a match, and made his way down. He thought he heard groans. As he went down, he found it was the concierge huddled in a corner.

"What is the matter?" he asked.

"Oh, my God, my God!" cried the concierge, "I knew they would do it. We are all blown to atoms!"

"Get up," said Dupre, "you're not hurt; come with me and see if we can be of any use."

"I'm afraid of another explosion," groaned the concierge.

"Nonsense! There's never a second. Come along."

They found some difficulty in getting outside, and then it was through a hole in the wall and not through the door. The lower hall was wrecked.

Dupre expected to find a crowd, but there was no one there. He did not realise how short a time had elapsed since the disaster. The policeman was on his hands and knees in the street, slowly getting up, like a man in a dream. Dupre ran to him, and helped him on his feet.

"Are you hurt?" he asked.

"I don't know," said the policeman, rubbing his head in his bewilderment.

"How was it done?"

"Oh, don't ask me. All at once there was a clap of thunder, and the next thing I was on my face in the street."

"Is your comrade inside?"

"Yes; he and M. Sonne and two customers."

"And the garcon, wasn't he there?" cried Dupre, with a note of disappointment in his voice.

The policeman didn't notice the disappointed tone, but answered--

"Oh, the garcon, of course."

"Ah," said Dupre, in a satisfied voice, "let us go in, and help them." Now the people had begun to gather in crowds, but kept at some distance from the cafe. "Dynamite! dynamite!" they said, in awed voices among themselves.

A detachment of police came mysteriously from somewhere. They drove the crowd still further back.

"What is this man doing here?" asked the Chief.

The policeman answered, "He's a friend of ours; he lives in the house."

"Oh," said the Chief.

"I was going in," said Dupre, "to find my friend, the officer, on duty in the cafe."

"Very well, come with us."

They found the policeman insensible under the debris, with a leg and both arms broken. Dupre helped to carry him out to the ambulance. M. Sonne was breathing when they found him, but died on the way to the hospital. The garcon had been blown to pieces.

The Chief thanked Dupre for his assistance.

They arrested many persons, but never discovered who blew up the Cafe Vernon, although it was surmised that some miscreant had left a bag containing an infernal machine with either the waiter or the proprietor.