It was after dinner, in the great house of Sir Henry Marquis in St. James's Square.

The talk had run on the value of women in criminal investigation; their skill as detective agents . . . the suitability of the feminine intelligence to the hard, accurate labor of concrete deductions.

It was the American Ambassadress, Lisa Lewis, who told the story.

It was a fairy night, and the thing was a fairy story.

The sun had merely gone behind a colored window. The whole vault of the heaven was white with stars. The road was like a ribbon winding through the hills. In little whispers, in the dark places, Marion told me it. We sat together in the tonneau of the motor. It was past midnight, of a heavenly September. We were coming in from a stately dinner at the Fanshaws'.

A fairy story is a nice, comfortable human affair. It's about a hero, and a thing no man could do, and a princess and a dragon. It tells how the hero found the task that was too big for other men, how he accomplished it, circumvented the dragon and won the princess.

The Arabian formula fitted snugly to the facts.

The great Dominion railroad, extending from Montreal into New York, was having a run of terrible luck; one frightful wreck followed another. Nobody could get the thing straightened out. Old Crewe, the railroad commissioner of New York, was relentless in pressing hard conditions on the road. Then out of the West, had come young Clinton Howard, big, tawny, virile, like the race of heroes. He had cleaned out the tangles, set the thing going, restored order and method; and the confidence of Canada was flowing back. Then Howard had made love to Marion in his persistent dominating fashion . . . . and here, with her whispered confession, was the fairy story ended.

Marion pointed her finger out north, where, far across the valley, a great country-house sat on the summit of a wooded hill.

"Clinton has discovered the Commissioner's secret, Sarah," she said. "The safety of the public isn't the only thing moving old Crewe to hammer the railroad. He pretends it is. But in fact he wishes to get control of the road in a bankrupt court."

She paused.

"Crewe is a Nietzsche creature. Victory is the only thing with him. Nothing else counts. The way the road was going he would have got it in the bankrupt court by now. He's howling `safety first' all over the country. `Negligence' is the big word in every report he issues. It won't do for Clinton to have an accident now that any degree of human foresight could have prevented."

"Well," I said, "the dragon will give the hero no further trouble. Dr. Martin told mother to-day that Mr. Crewe's mind had broken down, and they had brought him out from New York. He got up in a directors' meeting and tried to kill the president of the Pacific Trust Company, with a chair. He went suddenly mad, Dr. Martin said."

Marion put out her hands in an unconscious gesture.

"I am not surprised," she said. "That sort of temperament in the strain of a great struggle is apt to break down and attempt to gain its end by some act of direct violence."

Then she added:

"My grandfather says in his work on evidence that the human mind if dominated by a single idea will finally break out in some bizarre act. And he cites the case of the minister who, having maneuvered in vain to compass the death of the king by some sort of accident, finally undertook to kill him with an andiron."

She reflected a moment.

"I am afraid," she continued, "that the harm is already done. Crewe has set the whole country on the watch. Clinton says there simply must not be a slip anywhere now. The road must be safe; he must make it safe." She repeated her expression.

"An accident now that any sort of human foresight could prevent would ruin him."

"Oh, dear, it's an awful strain on us . . . on him," she corrected. "He simply can't be everywhere to see that everything is right and everybody careful. And besides, there's the finances of the road to keep in shape. He had to go to Montreal to-day to see about that."

She leaned over toward me in her eager interest.

"I don't see how he can sleep with the thing on him. The big trains must go through on time, and every workman and every piece of machinery mutt be right as a clock. I get in a panic. I asked him to-day if he thought he could run a railroad like that, like a machine, everything in place on the second, and he said, `Sure, Mike!'"

I laughed.

"`Sure, Mike,"' I said, "is the spirit in which the world is conquered."

And then the strange attraction of these two persons for one another arose before me; this big, crude, virile, direct son of the hustling West, and this delicate, refined, intellectual daughter of New England. The ancestors of the man had been the fighting and the building pioneer. And those of the girl, reflective people, ministers of the gospel and counselors at law. Marion's grandfather had been a writer on the law. Warfield on Evidence, had been the leading authority in this country. And this ambitious girl had taken a special course in college to fit her to revise her grandfather's great work. There was no grandson to undertake this labor, and she had gone about the task herself. She would not trust the great book to outside hands. A Warfield had written it, and a Warfield should keep the edition up. Her revision was now in the hands of a publisher in Boston, and it was sound and comprehensive, the critics said; the ablest textbook on circumstantial evidence in America. I looked in a sort of wonder at this girl, carried off her feet by a tawny barbarian!

Marion was absorbed in the thing; and I understood her anxiety. But the most pressing danger, she did not seem to realize.

It lay, I thought, in the revenge of a discharged workman. Clinton Howard had to drop any number of incompetent persons, and they wrote him all sorts of threatening letters, I had been told. With all the awful things that happen over the country some of these angry people might do anything. There are always some half-mad people.

She went on.

"But Clinton says the public is as just as Daniel. If he has an accident in the ordinary course of affairs the public will hold him for it. But if anything should happen that he could not help, the public will not hold him responsible."

I realized the force of that. What reasonable human care could prevent he must answer for, but the outrage of a criminal would not be taken in the public mind against him. On the contrary, the sympathy of the public would flow in. When the people feel that a man is making every effort for their welfare, the criminal act of an outsider brings them over wholly to his support. Profound interest carried Marion off her feet.

"I was in a panic the other day, and Clinton said, `Don't let rotten luck get your goat. I'm done if an engineer runs by a block, but nothing else can put it over on me'!"

She laughed with me at the direct, virile, idiom of young America in action.

An event interrupted the discourse. The motor took a sharp curve and a young man running across the road suddenly flung himself face, down in the grass beyond the curb.

"Is he hurt?" said Marion to the chauffeur.

"No, Miss, he's hiding, Miss," said the man, and we swept out of sight.

I thought it more likely that the creature was in liquor. In spite of the great country-houses, it was not good hunting-ground for the criminal class, during the season when everybody was about. The very number of servants, when a place is open, in a rather effective way, police it. Besides the young man looked like a sort of workman. One gets such impressions at a glance.

The motor descended the long hill toward the river and the flat valley. It hummed into the curves and hollows, through the pockets of chill air, and out again into the soft September night.

Then finally it swept out into the flat valley, and stopped with a grind of the emergency brake that caused the wheels to skid, ripping up the dust and gravel. For a moment in the jar and confusion we did not realize what had happened, then we saw a great locomotive lying on its side, and a line of Pullmans, sunk to the axles in the soft earth.

The whole "Montreal Express" was derailed, here in the flat land at the grade crossing. The thing had been done some time. The fire had been drawn from the engine; there was only a sputtering of steam. The passengers had been removed. A wrecking-car had come up from down the line. A telegrapher was setting up a little instrument on a box by the roadside. A lineman was climbing a pole to connect his wire. A track boss with a torch and a crew of men were coming up from an examination of the line littered with its wreck.

I hardly know what happened in the next few minutes. We were out of the motor and among the men almost before the car stopped.

No one had been hurt. The passenger-coaches were not turned over, and the engineer and fireman had jumped as the cab toppled. By the greatest good fortune the train had gone off the track in this low flat land almost level with the grade. Several things joined to avoid a terrible disaster; the flat ground that enabled the whole train to plow along upright until it stopped, the track lying flush with the highway where the engine went off, and the fact that trains must slow up for this grade crossing. Had there been an embankment, or a big ditch, or the train under its usual headway the wreck would have been a horror, for every wheel, from the engine to the last coach, had left the rails.

We were an excited group around the train's crew, when the trackman came up with his torch. Everybody asked the same question as the man approached.

"What caused the accident?"

"Spread rails," he said. "These big brutes," he pointed to the mammoth engine sprawling like a child's top on its side, the gigantic wheels in the air, "and these new steel coaches, are awful heavy. "There's an upgrade here. When they struck it, they just spread out the rails."

And he pushed his closed hands out before him, slowly apart, in illustration.

The man knew Marion, for he spoke directly to her in reply to our concerted query. Then he added "If you step down the track, Miss Warfield, I'll show you exactly how it happened."

We followed the big workman with his torch. Marion walked beside him, and I a few steps behind. The girl had been plunged, on the instant, headlong into the horror she feared, into the ruin that she had lain awake over - and yet she met it with no sign, except that grim stiffening of the figure that disaster brings, to persons of courage. She gave no attention to her exquisite gown. It was torn to pieces that night; my own was a ruin. The crushing effect of this disaster swept out every trivial thing.

In a moment we saw how the accident happened, the workman lighting the sweep of track with his torch. Here were the plow marks on the wooden cross ties, where the wheels had run after they left the rails. One saw instantly that the thing happened precisely as the workman explained it. When the heavy engine struck the up-grade, the rails had spread, the wheels had gone down on the cross-ties, and the whole train was derailed.

I saw it with a sickening realization of the fact.

Marion took the workman's torch and went over the short piece of track on which the thing had happened. All the evidences of the accident were within a short distance. The track was not torn up When the thing began. There was only the displaced rail pushed away, and the plow marks of the wheels on the ties. The spread rails had merely switched the train off the track onto the level of the highway roadbed into the flat field.

Marion and the workman had gone a little way down the track. I was quite alone at the point of accident, when suddenly some one caught my hand.

I was so startled that I very nearly screamed. The thing happened so swiftly, with no word.

There behind me was a woman, an old foreign woman, a peasant from some land of southern Europe. She had my hand huddled up to her mouth.

And she began to speak, bending her aged body, and with every expression of respect.

"Ah, Contessa, he is not do it, my Umberto. He is run away in fear to hide in the Barrington quarry. It is accident. It is the doing of the good God. Ah, Contessa," and her old lips dabbed against my hand. "I beg him to not go, but he is discharge; an' he make the threat like the great fool. Ah, Contessa, Contessa," and she went over the words with absurd repetition, "believe it is by chance, believe it is the doing of the good God, I pray you." And so she ran on in her quaint old-world words.

Instantly I remembered the man lying by the roadside, and the threats of discharged workmen.

I told her the thing was a clean accident, and tried to show her how it came about. She was effusive in gratitude for my belief. But she seemed concerned about Marion and the others. She did not go away; she went over and sat down beside the track.

Presently the others returned. They were so engrossed that they did not notice my adventure or the aged woman seated on the ground.

Marion was putting questions to the workman.

"There was no obstruction on the track?"

"No, Miss."

"The engineer was watching?"

"Yes, Miss Warfield, he had to slow up and be careful about the crossing. There is no curve on this grade, he could see every foot of the way. The track was clear and in place, and he was watching it. There was nothing on it. - The rails simply spread under the weight of the engine."

And he began to comment on the excessive size and weight of the huge modern passenger engine.

"The brute drove the rails apart," he said, "that's all there is to it."

"Was the track in repair?" said Marion.

"It was patrolled to-day, Miss, and it was all in shape."

Then he repeated:

"The big engine just pushed the rails out."

"But the road is built for this type of engine," said Marion.

"Yes, Miss Warfield," replied the man, "it's supposed to be, but every roadbed gets a spread rail sometimes."

Then he added:

"It has to be mighty solid to hold these hundred ton engines on the rails at sixty miles an hour."

"It does hold them," said Marion.

"Yes, Miss Warfield, usually," said the man.

"Then why should it fail here?"

The man's big grimy face wrinkled into a sort of smile.

"Now, Miss Warfield," he said, "if we knew why an accident was likely to happen at one place more than another we wouldn't have any wrecks."

"Precisely," replied Marion, "but isn't it peculiar that the track should spread at the synclinal of this grade with the train running at a reduced speed, when it holds on the synclinal of other grades with the train running at full speed?"

The man's big face continued to smile.

"All accidents are peculiar, Miss Warfield; that's what makes them accidents."

"But," said Marion, "is not the aspect of these peculiarities indicatory of either a natural event or one designed by a human intelligence?"

The man fingered his torch.

"Mighty strange things happen, Miss Warfield. I've seen a train go over into a canal and one coach lodge against a tree that was standing exactly in the right place to save it. And I've seen a passenger engine run by a signal and through a block and knock a single car out of a passing freight-train, at a crossing, and that car be the very one that the freight train's brakeman had just reached on his way to the caboose; just like somebody had timed it all, to the second, to kill him. And I've seen a whole wreck piled up, as high as a house, on top of a man, and the man not scratched."

"I do not mean the coincidence of accident," said Marion, "that is a mystery beyond us; what I mean is that there must be an organic difference in the indicatory signs of a thing as it happens in the course of nature, and as it happens by human arrangement."

The trackman was a person accustomed to the reality and not the theory of things.

"I don't see how the accident would have been any different," he said, "if somebody had put that tree in the right spot to catch the coach; or timed the minute with a stop-watch to kill that brakeman; or piled that wreck on the man so it wouldn't hurt him. The result would have been just the same."

"The result would have been the same," replied Marion, "but the arrangement of events would have been different."

"Just what way different, Miss Warfield?" said the man.

"We cannot formulate an iron rule about that," replied Marion, "but as a general thing catastrophes in nature seem to lack a motive, and their contributing events are not forced."

The big trackman was a person of sound practical sense. He knew what Marion was after, but he was confused by the unfamiliar terms in which the idea was stated.

"It's mighty hard to figure out," he said. "Of course, when you find an obstruction on the track or a crowbar under a rail, or some plain thing, you know."

Then he added:

"You've got to figure out a wreck from what seems likely."

"There you have it exactly," said Marion. "You must begin your investigation from what your common experience indicates is likely to happen. Now, your experience indicates that the rails of a track sometimes spread under these heavy engines."

"Yes, Miss Warfield."

"And your experience indicates that this is more likely to happen at the first rise of the synclinal on a grade than anywhere on a straight track."

"Yes, Miss Warfield."

"Good!" said Marion, "so far. But does not your experience also indicate that such an accident usually happens when the train is running at a high rate of speed?"

"Yes, Miss Warfield," said the man. "It's far more likely to happen then, because the engine strikes the rails at the first rise of the grade with more force. Naturally a thing hits harder when it's going . . . But it might happen with a slow train."

Marion made a gesture as of one rejecting the man's final sentence.

"When you turn that way," she said, "you at once leave the lines of greatest probability. Why should you follow the preponderance of common experience on two features here, and turn aside from it on the third feature?"

"Because the thing happened," replied the man, with the directness of those practical persons who drive through to the fact.

"That is to say an unlikely thing happened!" Marion made a decisive gesture with her clenched fingers. "Thus, the inquiry, beginning with two consistent elements, now comes up against one that is inconsistent."

"But not impossible," said the man.

"Possible," said Marion, "but not likely. Not to be expected, not in line with the preponderance of common experience; therefore, not to be passed. We have got to stop here and try to find out why this track spread under a slow train."

"But we see it spread, Miss Warfield," said the trackman with a conclusive gesture.

"True," replied Marion, "we see that it did spread, under this condition, but why?"

The old woman sitting beside the track seemed to realize what was under way; for she rose and came over to where I stood. "Contessa," she whispered, in those quaint, old world words, "do not reveal, what I have tol'. I pray you!"

And she followed me across the few steps to where the others stood.

I did not answer. I stood like one in some Hellenic drama, between two tragic figures. The love of woman lay in the solution of this problem - in the beginning and at the end of life.

Marion and the big track boss continued with this woman looking on.

I feared to speak or move; the thing was like a sort of trap, set with ghastly cunning, by some evil Fate. The ruin of a woman it would have. And perhaps on the vast level plain where it evilly dwelt, through its hard all-seeing eyes, the ruin and the sorrow either way would be precisely equal. How could I, then, lay a finger on the scale.

"Now," said Marion, "when the engine reached this point on the track, one of the rails gave way first."

The big workman looked steadily at her.

"How do you know that, Miss Warfield?" he said.

"Because," replied Marion, "the marks of the wheels of the locomotive on the ties are found, in the beginning, only on one side of the track, showing that the rail on that side gave way, when the engine struck it, and the other rail for some distance bore the weight of the train."

She illustrated with her hands.

"When the one rail was pushed out, the wheels on that side went down and continued on the ties, while the wheels on the other side went ahead on the firm rail."

The workman saw it.

"That's true, Miss Warfield," he said, "one rail sometimes spreads and the other holds solid."

Marion was absorbed in the problem.

"But why should the one rail give way like this and its companion hold?"

"One of the rails might not be as solid as the other," said the man.

"But it should have been nearly as solid," replied "Marion. "This piece of track, you tell me, was examined to-day; the ties are equally sound on both sides, the rail is the same weight. We have the right to conclude then that each of these rails was about in the same condition. I do not say precisely, in the same condition. Now, it is true that under these conditions one of the rails might have been pushed out of alignment before the other. We can grant a certain factor of difference, a certain reasonable factor of difference. But not a great factor of difference. We have a right to conclude that one rail would give way before the other. But not that one would very readily give way before the other. For some reason this particular rail did give way, much more readily than it ought to have done."

The trackman was listening with the greatest interest.

"Just how do you know that, Miss Warfield?" he said.

"Why," replied Marion, "don't you see, from the mark on the ties, that the engine wheels left the rail almost at the moment they struck it. The marks of the wheels commence on the second tie ahead of the beginning of the rail. Therefore, this rail, for some reason, was more easily pushed out of alignment than it should have been. What was the reason?"

The track boss reflected.

"You see, Miss Warfield, this place is the beginning of an up-grade, the engine was coming down a long grade toward it, so when this train struck the first rails of the up-grade it struck it just like you'd drive in a wedge, and the hundred-ton brute of an engine jammed this rail out of alignment. That's all there is to it. When the rail sprung the wheels went down on the ties on that side and the train was ditched."

"It was a clean accident, then, you think?" said Marion.

"Sure, Miss Warfield," replied the man. "If anybody had tried to move that rail out of alignment, he would have to disconnect it at the other end, that is, take off the plate that joins it to the next rail. That would leave the end of the rail clean, with no broken plate. But the end of the rail is bent and the plate is twisted off. We looked at that the first thing. Nobody could twist that plate off. The engine did it when it left the track.

"You see, Miss Warfield, the weight of the engine, like a wedge, simply forced one of these rails out of alignment. Don't you understand how a hundred ton wedge driven against the track, at the start of an upgrade, could do it?"

The old peasant woman stood behind the track boss. The thing was a sort of awful game. She did not speak, but the vicissitudes of the inquiry advanced her, or retired her, with the effect of points, won or lost.

"I understand perfectly," replied Marion, "how the impact of the heavy engine might drive both rails out of alignment, if they offered an equal resistance, or one of them out if it offered a less resistance. This is straight track. The wedge would go in even. It should have spread the rails equally. That's the probable thing. But instead it did the improbable thing; it spread one. I hold the improbable thing always in question. Human knowledge is built up on that postulate.

"True, a certain factor of difference in conditions must be allowed, as I have said, but an excessive factor cannot be allowed. We have got to find it, or discard human reason as an implement for getting at the truth."

Again the big track boss smashed through the niceties of logic.

"These things happen all the time, Miss War. field. You can't figure it out."

"One ought to be able to determine it,"' replied the girl.

The track boss shook his head.

"We can't tell what made that rail give."

"Of course, we can tell," said Marion. "It gave because it was weakened."

"But what weakened it?" replied the man. "You can't tell that? The rail's sound."

"There could be only two causes," said Marion. "It was either weakened by a natural agency or a human agency."

The track boss made an annoyed gesture, like a practical person vexed with the refinements of a theorist.

"But how are you going to tell?"

"Now," said Marion, "there is always a point as you follow a thing down, where the human design in it must appear, if there is a human design in it. The human mind can falsify events within a limited area. But if one keeps moving out, as from a center, he will find somewhere this point at which intelligence is no longer able to imitate the aspect of the result of natural forces . . . I think we have reached it."

She paused and drove her query at the track boss.

"The spikes on the outside of this rail held it in place, did they not?"

"Yes, Miss Warfield."

"Did the impact of the engine force these spikes out of the ties?"

"Yes, Miss Warfield, it forced them out."

"How do you know it forced them out?"

"Well, Miss Warfield," said the man, pointing to the rail and the denuded cross-ties, don't you see they're out?"

"I see that they are out," replied Marion, "but I do not yet see that they have been forced out."

She moved a step closer to the track boss and her voice hardened. "If these spikes were forced out by the impact of the engine, we ought to find torn spike holes inclining toward the end of the crossties. . . . Look!"

The big practical workman suddenly realized what the girl meant.

He stooped over and began to flash his torch along the end of the ties. We crowded against him. Every one of the spike holes, for the entire length of the rail, was straight and clean. The man seized one of the spikes and scrutinized it under his torch.

Then he stood up. For a moment he did not speak. He merely looked at Marion. "It's the holy truth!" he said. "Somebody pulled these spikes with a clawbar. That weakened the rail, and she bowed out when the engine struck her."

Then he turned around, and shouted down the track to his crew. "Hey, boys! Spread out along the right of way and see if you can't find a claw-bar. The devils that do these tricks always throw away their tools."

We stood together in a little tragic group. The old peasant woman came over to where I stood, she walked with a dead, wooden step. "Contessa," she whispered, her old lips against my hand. "You will save him?"

And suddenly with a wild human resentment, I longed to cut a way out of the trap of this Fatality; to force its ruthless decree into a sort of equity, if I could do it.

"Yes," I said, "I will save him!"

It was an impulse with no plan behind it. But the dabbing of the withered mouth on my fingers was like actual physical contact with a human heart.

For a moment she looked at me as one among the damned might look at Michael. Then she went slowly away, down through the wooded copse of the meadow. And I turned about to meet Marion. I knew that she was now after the identity of the wrecker, and I faced her to foul her lines.

"This is not the work of one with murder in his heart," she said "A criminal agent set on a ruthless destruction of property and life would have drawn these spikes on a trestle or an embankment, at a point where the train would be running at high speed."

She paused for a moment, then she went on speaking to me as though she merely uttered her mental comment to herself.

"These spikes are drawn at a point where the train slows down for a crossing and precisely where the engine would go off onto the hard road-bed of the highway into a level meadow. That means some one planned this wreck to result in the least destruction of life and property possible. Now, what class of persons could be after the effect of a wreck, exclusive of a loss of life?"

I saw where her relentless deductions would presently lead. This was precisely the result that a discharged foreign workman would seek in his reprisal. This man would have hot blood, the southern Europe instinct for revenge, but with such a mother, no mere lust to kill. I tried to divert her from the fugitive.

"Train robbers," I said. "I wonder what was in the express-car?"

She very nearly laughed. "This is New York," she said, "not Arizona. And besides there was no express-car. This thing was done by somebody who wanted the effect of a wreck, and nothing else, and it was done by some one who knew about railroads.

"Now, what class of persons who know about railroads could be moved by that motive?"

She was driving straight now at the boy I stood to cover. At another step she would name the class. Discharged workmen would know about railroads; they would be interested to show how less efficient the road was without them; and a desperate one might plan such a wreck as a demonstration. If so, he would wish only the effect of the wreck, and not loss of life. Marion was going dead ahead on the right line, in another moment she would remember the man we passed, and the "black band" letters. I made a final desperate effort to divert her.

"Come along!" I called, "the first thing to do now is to talk with Clinton Howard. The nearest telephone will be at Crewe's house on the hill."

And it won.

"Lisa!" she cried, "you're right I We must tell him at once."

We hurried down the track to the motor-car. I had gained a little time. But how could I keep my promise. And the next moment the problem became more difficult. The track boss came up with a short iron bar that his men had found in the weeds along the right of way.

"There's the claw-bar, that the devil done it with," he said.

"You can tell it's just been handled by the way the rust's rubbed off."

It was conclusive evidence. Everybody could see how the workman's hands, as he labored with the claw-bar to draw the spikes, had cleaned off the rust.

I hurried the motor away. We raced up the long winding road to Crewe's country-house, sitting like a feudal castle on the summit. And I wondered, at every moment, how I could keep my promise. The boy was a criminal, deserving to be hanged, no doubt, but the naked mother's heart that had dabbed against my fingers overwhelmed me.

Almost in a flash, I thought, we were in the grounds and before Crewe's house. Then I noticed lights and a confusion of voices. No one came to meet us. And we got out of the motor and went in through the open door. We found a group of excited servants. An old butler began to stammer to Marion.

"It was his heart, Miss . . . the doctor warned the attendants. But he got away to-night. It was overexertion, Miss. He fell just now as the attendants brought him in." And he flung open the library door.

On a leather couch illumined by the brilliant light, Crewe lay; his massive relentless face with the great bowed nose, like the iron cast of what Marion had called a Nietzsche creature, motionless in death; his arms straight beside him with the great gloved hands open.

And all at once, at the sight, with a heavenly inspiration, I kept my promise.

"Look!" I cried. "Oh, everybody, how the palms of his gloves are covered with rust!"