The thing that keeps life keen is that you can never figure out what’s ahead.

There’s always a surprise around the corner. The thing changes on you, to use an expression of the vernacular. One begins in an English drawing-room and winds up on the Gobi Desert. You never know where the road’s going. Take it in big things, or take it in the trivialities of life—it’s the same system.

But I am not going to lecture on philosophy; I am going to cite a case—a case that had an immense surprise in it to me, and a series of events that started out in one direction and concluded in another. I saw them start simply enough, but they “changed on me,” to keep our colloquialism.

I had just come down from Bar Harbor. I had an artificial diamond made in Germany, and I was looking for Walker. Walker is chief of the United States Secret Service, and he knows more about artificial stones than any other man in America, unless it is Bartoldi.

Gems are a fad with Walker, and a profession with Bartoldi.

I do not know which of these motive impulses moves a man to the higher efficiency. The keen man with the fad gets to be an expert, and the necessities of trade makes the other one. Anyway, I wanted to show my diamond to both of them.

I found Walker in the Forty-seventh National Bank on lower Fifth Avenue. He waved a recognition and went on with what he was saying to the cashier behind the grill:

“There was no robbery; that’s what puzzles me. How did they get the thing? It’s lucky the bank discovered that it was missing almost immediately and sent out the word. The package had just come in, and was lying on a shelf under the bookkeeper’s desk.... But how did they get it?”

And so I found Walker.

Nobody would ever have taken Walker for the chief of the government Secret Service. In appearance he was the last person any one would have picked out for a secret agent.

He looked like a practical person, and that is precisely what he was. You never could think that the man had any imagination; and he didn’t have any. At least, he didn’t have any imagination in the sense that we usually understand it. I suppose he had the kind of imagination that the inventor has, or the mathematician when he figures the orbit of the stars, or the engineer when he has to make some calculation on the stresses of a bridge.

I asked him to look at my diamond when he came out. His face took on a decided expression of interest.

“Go up and see Bartoldi,” he said. “I will be along in an hour.”

He added with a sort of smile:

“There is no leisure in my trade. Somebody’s always either robbing a national bank or trying to rob—boring from within or setting up some game on the outside.”

Then he laughed.

Now, that is how I happened to find Walker—just when I wanted to find him. By accident I stepped into something, as you would say.

Well, it was not explained to me. In fact, to say plain truth, behind a lot of courteous indirections, he put me out of the bank and sent me up to Bartoldi’s to await his coming in an hour. I do not mean that he ordered me out. He enticed me out; he edged me out, a good deal as one would do with a child that had wandered into a rather tense conference.

I went up to Bartoldi’s. Everybody knows where it is.

He has a mammoth place on Fifth Avenue, rather far up—the trade is going up. The big retailers saw that a dozen years ago. Bartoldi is not the greatest jewel dealer in the world, but he is one of the greatest. The greatest jewel dealer in the world is Mahadol in Bombay; then come Vanderdick in Amsterdam, and Hauseman in Paris.

It is a big shop, as I have said. But you know it—there is no reason to describe it here. A huge place with glass cases like every American shop, and the jewels displayed, as is the almost universal custom in America. Not like some of the foreign places, where you see only a square of black velvet, and the jewel, when you have named the kind you want, is brought out of a vault.

I was in this shop before the long counter that contains the tray of diamonds, when Bartoldi appeared.

Appeared is precisely the word; I did not see him until suddenly he was before me on the other side of the glass case.

He does not look like a jeweler. In fact, he does not look like anybody in active life. He is big and gaunt, and, in spite of the best tailor, he gives one the impression of an immense human body dried out in some desert. But he is alive, all right. I would like to see the man who could fool him about a jewel.

I showed him my diamond. It was a big diamond, unset, and I had it folded up in a piece of tissue paper.

He squinted at it between his thumb and finger.

“Good specimen,” he said, “first-class specimen. You can see the stratifications with your eye.”

He paused; then he went on:

“I never believed chemists could build up a diamond. Of course they build up rubies, and they do it cleverly, deuced cleverly, but you can always tell by the bubbles in them; they can’t get the bubbles out.”

He moved my diamond out a little farther from his eye.

“I suppose it is insufficient pressure. If they could get the angular cavities that are in corundum, they would be on the way; of course they would never get the steady glow of the genuine ruby. But they would fool the old ladies in a drawing-room.”

Then his voice went into a piping note.

“You would pass for the owner of rubies if you were rich enough to back up the hypothesis.”

He twisted my stone around in his fingers; then he pointed to the case under his hand, and set out a tray of diamonds.

He selected a table diamond as large as my false one and set above a platinum band. I could not have told the difference.

My diamond was worth four hundred dollars. Bartoldi said there was not a stone in the tray under five thousand dollars.

I stepped back to look at them from a little distance, about the distance one would observe a diamond on a woman’s hand at dinner across the table. I could not see any difference between the two stones. They could have been interchanged, and they would have fooled me at the distance. But they didn’t fool Bartoldi.

“Not much alike,” he said; “your stone has a sleek look.”

I did not see that. I told him I didn’t see it.

I knew that aspect of artificial stones, that appearance as if they were pressed instead of cut. But it was the aspect of artificial stones of a lower order than the one I had shown to Bartoldi. This one was cut, and it looked crisp to me, very nearly as crisp as the best one. But there is where the trained eye comes in. Walker knew it was false, and Bartoldi knew it instantly. He could see the stratifications with his eye.

I could see them with a good lens, but I could not see the sleek look, and I moved toward the tray on the counter to get a close view. I did not move directly ahead; I moved to one side—and I discovered two persons who had come into the shop behind me.

I took up my diamond, and stood out of the way at once. I had no wish to delay a customer. I was only idling with a laboratory diamond, and Bartoldi had to sell jewels to keep his shop going. I could not take up his time unless he happened to be at leisure.

The two persons who had come in at once attracted my attention. They would have attracted the attention of anybody, even if there had been nothing to follow. If one had chanced to observe them, one would have stopped and considered them anywhere.

One would have been forced to think about them. They would have stimulated one’s curiosity. No one could have passed those two persons without undertaking to formulate some explanation; and to me there was something more than their mere appearance.

In my mind there was a vague impression that I had seen them in some other place. I could not at the moment remember the place; it was what psychologists call subconscious, I suppose. At any rate it did not crystallize into a memory. But it remained as a sort of atmosphere behind the vivid impression they made on me.

The two persons were an old man and a girl. The two words go together, but the two persons did not go together in any sense. The girl was not past sixteen, and the man was past seventy. That would be all right, an old man and his granddaughter, you would say.

But it was not all right. That was just exactly the impression that was so cryingly conspicuous. It was not all right!

The man was very well dressed; everything about him was of the best quality, and distinguished—perhaps just a little too distinguished, a little too vivid. When one thought about it, one saw that he was dressed somewhat for a younger part. There was a bit of color, a suggestion of youth that the man did not have.

He was an old man, but he was a vigorous old man, and he had the air and manner of wealth about him. I can’t precisely point out these indicatory signs, but they were easily to be marked, and they are not often successfully assumed. I suppose a clever actor could do it. Walker used to say that the best actors were not on the stage; they were in Joliet.

Now, that is what the man looked like—one of the idle rich, grown old in an atmosphere of luxury. He ought to have had, as I figured him up, a town house, a country estate, a yacht, and very nearly every vice! His eyes, his bad mouth and his fat ears were good evidential signs. I thought I knew the type!

The girl filled me with a sort of wonder. She wore a little cheap hand-me-down dress that must have come from a village shop, and it looked as though she had slept in it. She had slept in it!

The sort of crumpled-up appearance of that cheap material could not be mistaken. She wore a straw hat lined with vivid color and loaded with soiled artificial flowers. Her shoes were run down a bit. She was generally soiled, as she would have been if she had traveled in a day coach and slept in her clothes—and that is precisely what she had done.

But all this could not obscure the fact that she was pretty, in a sort of way. She had a pliant figure, and the charms that go along with youth. Sleeping in one’s clothes, and the grime of a journey can’t obscure that. She was young, and she had what youth has.

Now you understand why I said that the two together puzzled me. Either alone would not attract a glance, and certainly not a line of speculation. But the two together, as I have insisted, called upon you for an explanation.

They puzzled me but they did not puzzle Bartoldi. I suppose he understood it quicker than I. I understood it pretty quickly, just as you have, no doubt, understood it all along, and as Bartoldi understood it at a glance.

They came up to the glass counter, and the man asked to see a diamond ring.

The girl did not look up. She did not say anything. She seemed to wish to get as far as possible under the soiled hat.

Bartoldi set out some trays beside the one already on the table. The old man moved a little to one side and the girl came quite close to the glass counter. She bent her head down over the stones as though she wished to see the rings and at the same time keep under cover of the soiled hat.

She did not say a word. But she knew precisely what she wanted, for she suddenly put out her hand and picked up the table diamond that had lain beside my artificial stone on the glass case. She slipped the stone on her finger and stepped back as though to be hidden a little by the old man.

I got a surprise.

“Gad,” I said to myself, “big wages! Will he stand for it?”

Well, he did stand for it. He was a royal old sport; I will say that for him.

Bartoldi said the price was five thousand dollars, and the old boy never turned an eyelash. He made a careless gesture. I don’t think he even O.K.’d the thing with a word.

He took a flat leather case out of his pocket, got out a draft, asked Bartoldi for a pen, or rather indicated the wish for a pen with a fiddling of his fingers, and when he got it, indorsed the draft. Then he showed Bartoldi a letter that was in the envelope that had contained the draft.

I followed them to the door. There was a taxicab waiting; they got in and went up the Avenue.

That type of man ought to have a house somewhere on the Avenue; it was August; the house would be closed; I began to put things together.

I was standing there when Walker came up. I hailed him.

“Walker,” I said, “you got here a moment too late. You see that taxicab?”

He made a little whimsical gesture.

“I see everything,” he said, “that the devil puts out to annoy me; what’s in the taxicab?”

“There’s a case in it,” I said, “for the District Court of the United States, on the criminal side, or I’m a poor detective.”

“All detectives are poor,” said Walker. “If they were rich, they would have a town house, a country place and a string of hunters.”

“Well,” I said, “that’s what the old boy in the taxicab has got; and he’s got something else that the United States doesn’t allow him to take across a state line.”

Walker looked at me queerly. He put the tip of his finger to his forehead.

“Touch of the heat?”

“Look here,” I said, “isn’t this sort of thing just as much in your line of duty as trying to prevent the crooked cashier from boring from within? Isn’t the United States by a fairly recent statute, helping virtue to evade the dragon?”

Walker’s face wrinkled into a twisted smile.

“It’s helping the clever fille de joie to levy a little blackmail on the side.”

“Wrong dope, in this instance,” I said.

I began to describe to him the incident and the two persons. I described them carefully, minutely, and he listened without a word and without a motion. He stood perfectly still, there in the hot street before Bartoldi’s mammoth shop.

But his manner had changed. He had now, I noted from the very impassive aspect of the man, a deep, a profound, a moving interest in this affair. He cursed softly as though he chopped the words with his teeth.

“Ten minutes too late!” he said. “Where did they go?”

Walker was motionless for a moment, his head down, his eyes narrowed in a profound reflection.

I interrupted him with a repetition of his words.

“Ten minutes too late!” I said. “You are two minutes too late. The taxicab has hardly disappeared in the traffic yonder.”

I pointed up the Avenue. Walker did not look up.

“I was thinking of Bartoldi,” he said. “I am ten minutes too late for Bartoldi.”

“That’s right,” I said. “Bartoldi could have told you who this man was. He must have known him.”

“Oh, no,” said Walker. “Bartoldi didn’t know him.”

I was astonished.

“Surely Bartoldi knew him,” I said.

Walker’s voice became a sort of drawl.

“Surely he did not know him. Bartoldi would not have been a party to this man’s criminal adventures.”

I laughed.

“What does Bartoldi care about criminal adventures? He’s a dealer in jewels.”

“He will care about this criminal adventure,” said Walker.

Then he looked suddenly at me.

“Where do you think they went?”

I told him what I thought. This type of person would have a house on the Avenue; it would be closed in August.

Walker shook his head.

“I think I know where they have gone,” he said.

Again I looked at him in astonishment.

“Then you know who this man is?”

Walker replied with an abrupt query:

“Did you see the inside of his hand—the right hand? That was the thing to see.”

“How about the girl?” I replied, for Walker’s indirections were putting me on my mettle. “Her hand will be the thing to see; it’s got Bartoldi’s diamond on it.”

He looked up rather vaguely.

“I am puzzled about the girl; I do not understand what the girl has to do with it.”

I laughed.

“Bartoldi understood,” I said.

“Bartoldi!”

Walker seemed to bounce out of his reflection.

“The devil! We’ve got to get back his diamond.”

He darted suddenly out to the traffic of the Avenue, hailed a taxicab and beckoned me to get in with him.

I got in and we went up Fifth Avenue. We were held in a jam of vehicles a block or two farther on.

“And so,” I said, “you think the girl is a nice little country cousin, an esteemed relative—esteemed to the tune of a five-thousand-dollar diamond?”

Walker was fingering his face in reflection.

“Nonsense!” he said. “The girl’s no relation to him.”

“Then why the five-thousand-dollar diamond?”

“That’s what I would like to know,” said Walker.

I laughed. The thing was too absurd.

“If the wage of a sin is a five-thousand-dollar diamond, there’s got to be the sin to earn it. That old sport was not taking any chance on getting the value of his money.”

“O. K.,” said Walker.

“Then you think he has been paid for it?” I said.

“Surely,” said Walker, “that man has been paid for it.”

The taxicab turned out of the Avenue presently when the jam of vehicles was released, and stopped before the Grand Central Station.

Walker paused a moment when we got down.

“If I put the thing together correctly,” he said, “they will be here. The girl came in for her diamond.... How she earned it puzzles me.... The man had to get through with it as quickly as he could.”

He made a little gesture.

“From the station to Bartoldi’s in a taxicab and back to the first train out—that would be his plan—to hurry.”

He added: “It was a risk, a big risk. But he had to take it. He couldn’t trust anybody; he had to do it himself.”

I looked at Walker with what I imagined was an ironical smile.

“Then he would not be guilty under the statute,” I said, “for he only brought the little baggage in to buy her a diamond.”

Walker seemed in a sort of reflection.

“Oh, yes,” he said, “he is guilty.”

“Then you want him?” I asked.

Walker suddenly looked at me with his eyes wide.

“Surely,” he said.

“Then why don’t you hurry?” I demanded.

He looked at me with a leisurely interest.

“If he’s here,” he said, “he can’t get out. I’ve got three of the best agents of the Department in there—sent them up when I started to Bartoldi’s to meet you.”

“But how would they know him?” I asked.

“They would know him by a scar in his hand,” replied Walker.

“They ought to know him by a girl on his arm,” I said.

Walker’s voice became reflective.

“I wonder if she could be his granddaughter, after all!”

I laughed. That laugh was like the key to a memory. I at once remembered where I had seen this man and the girl.

It was at the end of the path that follows the sea south at Bar Harbor. There is a great house where the path ends. It was closed; the shutters were up, and the grounds only casually kept; I remembered it now. I had undertaken one afternoon to get through from this sea-path to the village street, and had wandered into an immense sunken garden. I was making no sound.

The grass and leaves had covered the paths; it was very still, and presently I heard the murmur of voices. I wondered who could be here, for as I have said, the place was closed, and I was discovering that there was no way through to the village street. I went forward a few steps, and beyond me, standing in an angle of the garden, obscured by an immense flowering vine, were this old man and this girl.

I remembered the scene perfectly, now that I had the key to it.

The old man was speaking in a low voice, as though he urged something, offered something, and the girl was listening in the attitude in which I had observed her this afternoon, her head down, her arms hanging. I had gone out quietly; I remember the explanation that presented itself. The old man must be the owner of the place, and the girl a keeper’s daughter, perhaps. The memory bore out my impression, the impression which I received to-day and the impression which had evidently convinced Bartoldi.

I told it all to Walker, very carefully and in detail, as we went into the great lobby and down to the train exits. Walker caught my arm in his big hand.

“That explains it,” he commented.

Then he stopped abruptly.

“By the way,” he said, as though it had just occurred to him and he had now leisure to think about it, “let me have a look at that artificial diamond.”

I took the piece of tissue paper out of my waistcoat pocket and handed it to him. He unfolded the paper, took the diamond out and retained it in his hand. We crossed through the throngs of people everywhere grouped about in the great station, to the exit indicating the evening train to Bar Harbor. We entered the little group, and I realized suddenly that we were close behind the old man and the girl. They were facing toward the gate.

Suddenly Walker opened his hand and dropped my diamond to the floor. It clattered at the feet of the girl, and Walker stooped swiftly and picked it up.

“Your daughter,” he said, speaking to the old man, “has dropped the setting out of her ring; permit me to return it.”

The man turned instantly like a trapped animal. For a moment both of his hands went into the pockets of his coat, and for an instant his face was uncertain, vague, deadly; then he put out his hand for the diamond.

Walker gave it to him and turned to me.

“Perhaps,” he said, “we had better see if the trunks got on. We have nearly ten minutes to wait.”

And he walked away toward the great stair leading to the baggage room.

The girl did not move; she did not speak; she remained as she had stood in Bartoldi’s shop, her head down, concealed as far as she was able to conceal it, under the drooping hat loaded with soiled roses. Walker was crossing toward the great stair in his long stride and I hurrying in my astonishment to overtake him.

“The devil, man!” I cried when I came up. “Why did you give him my diamond?”

“I wanted to see if there was a scar in his hand,” said Walker. “He had it.”

“Then you know him?”

“Surely,” said Walker.

“Aren’t you going to arrest him?”

Walker had returned to his careless manner.

“No,” he said, “I am not going to arrest him. You saw his hands go into his pockets. There would have been a lot of people killed if it hadn’t been for your diamond. It’s lucky I thought of it; besides, I had to see the inside of his hand.”

“But my diamond,” I said, “when will I get it?”

Walker continued in his leisurely drawl:

“You will get your diamond when Bartoldi gets his.”

“When will that be?” I insisted.

“Right now,” replied Walker.

Then he paused in his stride, took off his hat and extended it for a moment above his head like a tired person who would relax from the fatigue of travel.

Immediately three persons, two men and a woman between them, carrying bags, coats and the usual articles of travel, came out from the crowd pouring into the station from the street and crossed hurriedly into the group waiting at the entrance for the Bar Harbor train.

Then a dramatic thing happened.

I could see the old man clearly; he was watching Walker out of the tail of his eye, and he kept his hands in his pockets, but he was not watching the three persons who came into the group as though seeking the train for which he was bound; and as they passed, quicker than the eye, the man’s hands were seized, dragged out of his pockets and snapped into handcuffs. The pistols gripped in his hands were swept out; they fell to the floor.

“The devil!” I cried. “The old boy is the most dangerous Lothario I ever saw.”

Walker replied in his leisurely drawl:

“He’s the most dangerous bank swindler you ever saw.”

The girl had been questioned, and the thing was now clear. Walker explained it all on the way to Bartoldi’s in a taxicab. I had my diamond in my pocket, and Walker had Bartoldi’s to exchange for the forged draft. The old man was Vronsky, the most notorious forger in the world. He had bribed this girl, the janitress of the Empire Bank at Bar Harbor, to steal a book of blank drafts and some sheets of stationery. It was easy to do; the book of blanks was lying on the bookkeeper’s desk in the package as it had come from the printer, and the stationery had never been locked up.

With the blanks bearing the secret water mark of the bank, Vronsky was able to forge drafts on New York and place them, establishing his identity by a letter from the bank officials on this stationery, in which they said they were sending him the draft which he intended to pay out, and giving its amount and number.

“It was a clever scheme,” Walker added. “The secret water mark on the draft blanks would show that they were genuine—that’s what convinced Bartoldi; and the forged letter would show the identity of the man who undertook to place it. The forgery gave Vronsky no trouble; the problem was how to get the blanks and letter paper.”

“And he got them with a diamond,” I said.

Walker’s drawl lengthened.

“Precisely as we got him.”

And so this adventure opened with a diamond and closed with the arrest of one of the worst criminals in the world. What was it I wrote in the opening paragraph of this case? Go back and read it.