As the horses started up, Dorothy refuted Tom’s statement indignantly. “It isn’t a blind alley. It’s a good clue. We’ve run down practically every other line, and now we may as well try this. Everything points to the belief that ‘the man’ is a scientist of no slight ability. Whether he or some one else discovered his high power radio-active force, he must be a good man, or he wouldn’t be able to use it. Now, it seems probable to me that he was working with phosphorescent ink simply because it was the nearest at hand. A man engaged in research like that would be likely to have at least one assistant. I propose to find that assistant.”

“I’d like to see you do it,” said Tom doubtingly. “How would you go to work?”

“I’d advertise,” said Dorothy.

“Advertise,” remarked Tom. “Here’s the way to do it,—‘Wanted, the assistant of the man who is trying to stop all war.’”

“Of course not, stupid,” said Dorothy impatiently. “We’ll advertise for a man who has had some experience in making phosphorescent ink. That’s the line to work on. Don’t you see that since phosphorescent paint acts best with such energy as is given by radio-active substances, that he’s likely to have been using it. There’s such a close relation between phosphorescence and radioactivity, that a man might be working with both.”

“But where will you advertise?” I said. “How can you tell where the man has worked? How can you tell his nationality? I think he is an American, but no one can tell.”

“If you mean Dick Regnier,” exclaimed Dorothy, her eyes flashing, “you’re wrong. I’ve known him for years, and I know he is not the man. It takes just a touch of insanity that Dick never had, to do what ‘the man’ is doing. ‘The man’ must be practically a monomaniac on the subject.”

The bus stopped just as the Bank came in sight. Dorothy turned squarely in her seat and faced me. The seats around us happened to be empty. She looked at my somewhat guilty face and spoke emphatically.

“Jim Orrington, you don’t believe me, but it isn’t Dick Regnier.”

“Now, Dorothy,” I said, “look here. How did the letter get changed, unless it was done by Regnier that night at your cousin’s?”

“I don’t know,” she answered.

“Oh, come now,” said Tom. “Drop it. Here’s where we get off.”

We had drawn our money and had started away, when I suddenly thought of the mail. I turned back to the little window and asked if there were any letters for us which had not been forwarded. A few moments brought a big package, among them three or four bulky envelopes from the office. Hailing a cab, we read busily as we drove back to the Savoy. One long typewritten report I read with especial care, and handed over to Dorothy when she had finished her mail. She looked at me reproachfully, as she read the title. “And you never mentioned this at all.”

“I forgot all about it,” I answered. “I started that inquiry the day I was in prison. The night I got out, the Denckel letter came, and we’ve been so busy ever since that I completely forgot this.”

“Let’s hear it,” said Tom.

“Just read the condensed paragraph at the top,” I said. “That tells the whole story. You can read the rest at your leisure.” Dorothy began in her clear voice.

“Report on Mr. Richard Regnier. Richard Regnier is the son of the late Colonel Arthur Regnier of Savannah, Georgia. He was educated at private schools, and at Princeton. His residence is Savannah, but he has spent much time in England. He specialized in chemistry when in college, and published one paper after graduation on some rare chemical compounds. He has no regular occupation, has an independent income, and spends most of his time in various philanthropic works. Is a member of several organizations, such as the Peace Society, the Tuberculosis League, etc., and of four clubs. Complete details given below. Every effort has been made to obtain his present address, but not even his bankers know it. The only fact concerning this which could be obtained was that he sailed for Europe on the Hamburg-American line, the last of June, this present year. For details of this part of the investigation, see below.”

“Well, he didn’t do it; he isn’t doing it,” said Dorothy emphatically.

“He’s got the training for it,” said Tom reflectively.

“I am sure,” began Dorothy, but I broke in.

“What’s the use of discussing it now. We can’t get hold of Regnier, anyway, and your phosphorescent ink scheme seems the next scheme to try. Here we are at the Temple. Let’s go to one of my friends who is a solicitor here, and see if we can use his office as headquarters to see the applicants.” So the discussion ended.

A brief interview with my friend, and a short debate on the best method of procedure, brought us to certain conclusions. It was really just as possible that the man had worked in London as anywhere else, and we decided to advertise in six of the morning papers for three days, asking for a man who had had some experience with phosphorescent inks, and who was capable of assisting in a scientific examination with regard to them. Applicants were to meet at the office of my friend in the Middle Temple at three o’clock on the afternoon of the third day.

For two days and a half I spent my time watching the preparations for war, and urging forward the search for Regnier. He had completely dropped out of sight. No information of his whereabouts could be obtained, and when we met at the Temple on the afternoon of the third day, we were no further ahead.

At three o’clock the waiting room of the office was full, and a long line of men extended down the stairs. The crowd bore striking witness to the horde of unemployed seeking for even the slightest chance of employment. My friend’s clerks were in despair, but somehow they managed to evolve something like order from the mass, and one by one the applicants were admitted. After the first half dozen, we saw that they could be divided into three classes,—the men who knew nothing about science and nothing about any kind of ink, the men who knew something about ink but nothing about phosphorescent ink, and the men who had been laboratory assistants to various research followers. We divided them rapidly on this basis, and in an hour had dismissed all the members of classes one and two. There were left some ten others who had been assistants in research laboratories. One by one we examined these. They had worked in various lines; the first five in chemical researches; the last five in various physical and engineering lines. Try as we might, we could get no information from any of them with regard to phosphorescent ink, or with regard to any unusual work with radio-active energy.

The last man had been dismissed and we had sat down to afternoon tea with my friend, when we heard words in the outer office. The door opened and a clerk entered. “There’s one man more, sir,” he said, “I told him he was too late, but he’s quite insistent, sir. Will you care to see him?”

“Surely,” I said, and we all went out into the outer office. A tall, bent man with drooping mustache stood by the window. His gaunt face and threadbare clothes, neatly brushed though they were, showed an evident lack of prosperity.

“I ventured to insist, sir,” he said, addressing me, “as I have had quite a little experience in phosphorescent ink. It was only a year ago that I served in a laboratory where they were working with it, and while I was simply working under the direction of other people, I think I could work well along that line. I should try to do my best. I need a place.”

This looked more like the real thing. I waved towards Tom. He could run this end of the inquiry better than I.

“What’s your name?”

“George Swenton.”

“Where did you have your experience?” questioned Tom.

“With Doctor Heidenmuller, in his private research laboratory,” answered the man.

“What training have you had?”

“Not much. Only a few courses at the University of London. I was only the second assistant. I worked with Doctor Heidenmuller for four years, until he died six months ago. I have had no place since, sir.”

“Did your employer do anything with radio-active work?”

“Yes, sir. He died that way. He was killed, paralysed, you might say, while working with something in a locked room. He always did that work in a locked room.”

“What were the circumstances of his death?” asked Tom. The man hesitated and looked up somewhat fearfully.

“I don’t see what that has to do with phosphorescent ink,” he said. “The police went all into the matter of his death, and they said it was just death by paralysis.” He stopped and shut his mouth hard. Dorothy broke in.

“Mr. Swenton, here is the state of affairs. I don’t think my brother has made it quite plain. We are more interested in Dr. Heidenmuller’s radio-active work than in his phosphorescent paint. We have no question of you at all. We do not want to know anything which is not entirely right for us to know, but we do want to know all you feel you can rightly tell us of his work. I feel sure that my brother will be ready to employ you, if you can show that you have done this, and that you can do what he wants.”

The man’s face cleared. Dorothy’s words were more convincing than evidence. He reached into his pockets and drew forth a bunch of papers, which he gave to Tom, who rapidly ran through them.

“They’re all right,” he said, handing them back. “Now, if I give you twenty pounds a month for two months, will that be all right?”

A dull red rose in the man’s face as his eyes lighted. “It will mean everything to me, sir,” he said. “I’ve got a wife and a boy.”

Tom drew out his purse. “Here’s ten pounds to clinch the bargain,” and he handed him two five pound notes.

“I appreciate that more than I can say,” said the man, the tears welling up into his eyes with emotion. “Now, what did you want to know?”

“First about Dr. Heidenmuller’s apparatus, and then about his death.”

“I’m afraid I can’t tell you much of the apparatus. I never even saw it. It was in an inner room to which the doctor had the only key. I never was in the room till the day we broke down the door and took him out dead. There was no apparatus there then. It must have been removed.”

“How did the room look?” asked Dorothy.

“It was all bare. Nothing in it at all, except the wooden chair where he sat and a wooden table.”

“How about the walls and ceiling?”

“They were all of wood.”

“How about the locks on the door and windows?”

“That was a funny thing. They were of wood, too, though he had an iron key.”

“What did the doctor have in his pockets?”

“Four five-pound notes, no change, and his watch was gone. There was nothing in his watch pocket except a watch crystal. His keys were gone, too, and only the ribbon of his watch was left lying on the floor.”

“What did the doctors say about his death?”

“Straight paralysis, they said. I had been away for three days. He was around the laboratory for one day after I left, and the day after that he must have died. They said death was instantaneous.”

“Did the doctor leave any family?”

“None.”

“What became of his papers?”

“Nobody knows. He had scarcely any friends. His property went to a niece in Germany, and she came over to hunt for papers, but she found none.”

“What became of the other assistant?”

“He went back to Germany. He knew nothing more than I did, however.”

“Did the doctor have any friends who came to see him?”

“Very few. There was one American who came to see him now and then. I never knew his name or where he came from, nor did I know the name of the two or three German friends he had.”

“Anything else you think of?” asked Tom.

“Nothing else, I’m afraid,” answered Swenton.

Tom rose from his chair and paced up and down the room, his hands in his trousers pockets, his coat flung back. As he walked, Swenton, watching him, uttered an exclamation.

“I can tell you one thing about the American,” he said. “He wore a peculiar shaped pin on his waistcoat, such as you wear on your fob.”

Tom pulled up his fob with its Theta Sigma Rho pin. “There’s a good clue, anyway,” he said. “He must be a Theta Sigma Rho man.”

We could get nothing more from Swenton and, after directing him to call at the Savoy the next morning, we sent him away happy. As we came down the narrow stairs and out of the old arched passages of the Temple, Dorothy said, “Let’s walk up the embankment to the hotel. We can think better that way.”

We had gone half the distance, when she stopped. “Suppose we talk it over here,” and we stopped beside the parapet to discuss the matter.

“As I make it out,” said Tom, “Heidenmuller was the man who discovered the secret power which has been destroying the battleships, but he can’t be ‘the man,’ because he died before the first ship went down. Therefore he must have passed it on to some one else who is using it, possibly the American who was his friend, or one of the Germans. It strikes me that the next thing to do is to find an American in London who wears a Theta Sigma Rho pin.”

Instantly I startled the peaceful calm of the embankment, and made myself an object of suspicion to the neighboring bobby, by leaping in the air and clapping my hands together.

“Hamerly, by all that’s holy!” I cried. “You remember that fellow I took home that night you arrived, Dorothy?”

She nodded, her eyes gleaming with interest.

“He’s one of our men, and he had an acid stain on his coat. I’ll wager you he’s the American. I know where he lives and I’ve been up to see him once, but he was out. I’ll go up there right after dinner.”

“Do you think he’s ‘the man’?” asked Tom in excitement.

“I don’t see how he could be,” I said slowly. “‘The man’ was working in the Channel, when he was in the British Museum. But he’s surely the next man to interview.”

By eight I was in a hansom speeding towards Half-Moon Street. “Was Mr. Hamerly in?” He was, and met me half way down the stairs. “This is very good of you, Orrington,” he said. “I was very sorry to miss your last call.”

For some time we talked of various things, of college days, and of affairs at home. He had come over as a Rhodes scholar and, having a little money left him while at Oxford, had gone on in London after graduation, leading a life of quiet study. As we talked, I sized my companion up. “A trifle grave but, after all, a sane, sterling fellow,” I decided, and I put my errand directly to him.

“You knew Dr. Heidenmuller,” I said abruptly.

“Yes, poor old chap,” he said calmly. “How did you happen to run across him?”

“I didn’t know him personally,” I said, “but I knew a man who did know him. One of our own men, Tom Haldane of Columbia, who is very greatly interested in the radio-active work which Dr. Heidenmuller was carrying on before his death, is here with me.”

Hamerly’s face filled with eagerness. His whole attitude changed. “Did Haldane know what he was doing?” he asked breathlessly.

“Not exactly,” I said.

“Well if he knows anything about it, I believe he knows one of the greatest things in modern science. The Doctor never told me anything about it, but I went into that room the day he was taken out dead, and ever since that time I’ve felt that he had found a force greater than anything yet obtained, and that that force killed him.” He paused. “I’ve never said that to anybody else, but Haldane is the man of all others to know it, and you might tell him that from me. He may be able to use it somehow. I can’t. I tried my best to get hold of some clue concerning it after Heidenmuller’s death, but it was absolutely useless. Do you think that Haldane has enough data to work it out?”

“Frankly, I don’t know,” I said.

“Except for two things, I should have said the secret died with him,” said Hamerly slowly.

I bent forward hanging on every word.

“I’ve never spoken of either, but,”—he paused, “you know this man who is trying to stop all war?”

I nodded.

“Well, from the way Heidenmuller’s room looked, and the way the things in his pockets were left, I’ve wondered if the man had not his secrets. Do you know,” he said, leaning forward, “there were no eyelets in his shoes when he was found. The crimps were in the leather of the strings, but the metal ends were gone. The lenses of his spectacles, without any mounting, were lying on the floor. The very filling of his teeth had gone. Why couldn’t a battleship disappear into its elemental parts the same way, all its living contents paralyzed by the shock, dying instantly and sinking below the waves. I’ve wondered more than once if the government sent down divers in Portsmouth harbor and if they did, what they found.”

There was just one thing to do. He held as much as we did of the secret. Perhaps he knew more. From beginning to end, I told the whole story of our search. As I went on, he grew more and more excited. As I paused towards the end, he broke in.

“The second thing fits in here, the reason why I believe the secret might not be lost. One day as I went into the laboratory, the Doctor’s assistant told me that he was in the inner room, but had left word for me to wait. I was extremely curious for no one had ever entered that inner room to my knowledge. The door opened at last, and a tall, dark man, an American I should say, came out of that closed room with the doctor. I never saw him before or since. Now, is he the man who got the secret, and with it is trying to stop all war?”

I was out of my seat with excitement. “I believe he is. Would you know him if you saw his photograph?”

“Surely,” said Hamerly.

I rose to go.

“Hold on,” exclaimed Hamerly, “I haven’t told you half yet.”

“Go on,” I said eagerly, seating myself once more.

“That first day, after I had made a rough examination, I started to go over the inner room inch by inch. At first I thought it was perfectly insulated by wood. There wasn’t a piece of metal nor even a piece of glass in it. Where the incandescent light came down, hung a bit of twisted cord, without a scrap of metal remaining. There was a length of insulating cloth, minus the wire it covered, lying on the floor. I went round and round, hunting for metal, but I could find none. There was a wooden shutter over the window, and no glass. I closed the door and walked over every inch of the room, trying to find any break whatsoever in the insulation. The only thing I could find was a faint glimmer, where the wooden window shutter did not quite join. I went outside and studied the place from the street. There was no appearance of anything unusual on the wall of the laboratory, excepting that the boarded window of the wooden room looked out like a rectangular unseeing eye. I crossed to the sidewalk just before the laboratory, and looked up and down the opposite wall. There was nothing unusual on that side, save two square places, side by side on the painted wall, which looked fresher than the wall around. I examined them more carefully, crossed and recrossed. The two spots were almost exactly opposite the lower end of the shuttered window where I had seen a slight chink of light, the only place where the insulation of wood was broken. I went up the stairs of the house opposite. It was a little tea shop. A wooden sign leaned against the wall beside the door. I picked it up. The screw holes and the whiter paint where the hinges had lain showed clear, but there was no metal about it. The proprietress bustled up to take my order and, as she saw me looking at the sign, broke into voluble explanation. ‘I should have put the sign back in its place, sir, but fairly didn’t dare to. It was a week come Tuesday when it fell. It’s God’s own mercy there wasn’t somebody killed, sir. And the strangest thing, too. I couldn’t find sight nor smell of the hinges and the rod where it hung. It must have pulled out of the wall, and somebody have picked up the iron, before I could get down, sir. Now isn’t that strange, sir?’

“It had fallen the day that Heidenmuller died.

“I went back into the laboratory and hunted over every square inch of it, but I found nothing. I stood there puzzling. If there had been some power that had killed Heidenmuller, there must have been some material substance in which it was kept. I had made the most careful inquiries about the things on his person and in the room. No one could tell me anything. Swenton and Griegen, the two assistants, were neither of them there, but the first one who had entered the room when the doctor’s body was found was a sharp-faced lad who acted as janitor. I had questioned him thoroughly, as I thought, but I resolved to see if he did not know more. I went to him again, and a lucky inspiration came to me. Holding a sovereign in my hand I remarked casually, ‘If there is any little personal memento of the doctor left, I should like very much to have it.’ The narrow eyes of the lad gleamed. He thrust his hand into his pocket, and drew out what was apparently a leather cigarette case, snatched the sovereign, and handed me the case. ‘Found h’it h’on the floor, h’after we took ’im h’out,’ he mumbled. ‘H’it’s the h’only think was there.’”

Hamerly rose as he spoke and walked to his desk. I followed, my heart pulsating with great leaps. He took from a drawer what seemed to be a pigskin cigarette case, cut in half. Hamerly held the two sections out on his hand. At the top was a queerly constructed valve,—the case was lined with a black substance that looked like rubber.

“I believe,” said Hamerly gravely, “that in this case there was some terrifically powerful substance, which killed Heidenmuller and destroyed all the metal in the wooden room, by escaping through the accidentally opened valve. I believe the man who is trying to stop all war uses the same dread agent. I believe, once the substance escapes and does its work, that it turns to a harmless gas, as hydrogen, once it has been exploded with oxygen, forms harmless water, or as the carbon of coal, which has blazed when united with the oxygen of the air becomes, after that union, inert carbon dioxide. You know, now, all I know. I’ve done all I could with it,” he ended, “Take it to Haldane.”

Dazed with the story, I could only thank him and take the case. We parted with a word of good will, and assurance of secrecy on his side.