AT ten-thirty, five tired and hungry people ascended the steps of No. 17 Walnut Street and rang the bell. It was not immediately answered. Then Drayton noticed that the door was not latched. They all entered and became aware that in the library on the right something unusual was going on. A gurgling, choking noise was punctuated by several thumps, followed by the crash of furniture violently overthrown.

Trenmore was first at the door. He flung it open and rushed inside. The room seemed empty. As the noises continued, however, Trenmore passed around the big reading table and stooping over plucked his man, Martin, from the prostrate body of an unknown antagonist. He did it with the air of one who separates his bull pup from the mangled corpse of the neighbor’s Pomeranian. With a sad, disgusted face Terry glanced from the pugnacious one to the figure on the floor.

“Ah now, boy,” he demanded, “are you not ashamed to be choking a man old enough to be your own grand-dad?” Then he dropped Martin, with an exclamation. “Sure, ’tis my old friend the little collector man!”

“Mr. Trenmore,” began Martin in excited self-defense, “he come in here and he—”

“Never mind what he did till I count what’s left of the pieces, my boy. I take back what I said, though. Be he alive or dead, the old rascal’s got no more than was coming to him.”

Kneeling down, while the rest gathered in an interested group, he put his hand to the man’s heart. He was an elderly, smooth-shaven, gray-haired person, with sharp, clean-cut features. The forehead was high and sloping, the mouth thin and tight-pressed even in unconsciousness. He was well dressed, and a gold pince-nez lay on the floor near by, miraculously unbroken.

“He’s all right,” announced Trenmore. “Martin, a drop of liquor now and we’ll have the old scoundrel up and able for an explanation.”

His prophecy proved correct. Five minutes later the gray-haired collector sat in an armchair, shaken but able to talk and be talked to.

“And now,” said Trenmore, “I’ll ask you, Martin, to tell your share in this, and then you’ll go out and you’ll get everything in the house that is eatable and you’ll set it out in the dining room, for it’s starved to death we are, every one of us.”

“Yes, Mr. Trenmore, I’ll tend to it. This old man broke in on me about half an hour ago. He asked for you, Sir. I told him you’d been out since this morning—”

“This morning!” The exclamation broke from three pairs of lips simultaneously. Martin stared.

“Never mind,” said Terry hastily. “And then?”

“He wanted to know where you were. I said I didn’t know, as you didn’t say anything to me. And then we got talking and—I’m sorry, sir—but I let out that it seemed mighty queer, your going that way. And then he asked me questions about where I’d last seen you and all that. I told him about finding this gray stuff—it’s wrapped up in that newspaper on the table, sir—and not knowing what it was or whether you wanted it kept or thrown out.

“And then—honest, I don’t know how he did it, but he got me to show it to him. I brought it in here. And then he said I’d never see you again, and would I sell him the stuff. I said no, of course. Then he pulled a gun on me—here it is—and I jumped on him—and then you came in. I didn’t want to hurt the old guy, but he got me wild and—”

“That’s all right, Martin. You did very well, but don’t ever be doing any of it again. Now hurry up that supper. What’s coming next would likely strain your poor brain. Get along with you.”

Reluctantly, Martin vanished kitchenward. The rest of the company pulled up chairs and made themselves comfortable. For a time they found the captive of Martin’s prowess inclined to an attitude of silent defiance. Upon Terry’s threat, however, to turn him over to the police on charges of housebreaking, he expressed a willingness to listen to reason. Bertram’s presence had a very chastening effect. He knew the burglar for one of the men he had hired to steal the Cerberus, and realized that should his former accomplice go on the stand, his testimony, together with the attack on Martin, would mean penitentiary stripes for himself.

“By the way,” Drayton broke in, picking up the newspaper package which contained the Dust of Purgatory and weighing it in his hand, “did you ever ask Bertram, Terry, if he knew what had become of the vial this was in?”

The burglar started and flushed. “Say, I done a mean trick then. I didn’t mean to keep the thing, but you left it laying on your bureau that day at the Belleclaire, Mr. Trenmore, and I—well, I took it along. I give it to Skidoo here for a keepsake. I didn’t have anything else pretty to give her. But she’s a straight girl and I shouldn’t’ve done it. Skidoo, have you got that bottle I give you for bath salts?”

“Sure.” No. 23000 promptly produced it from her sweater pocket. “Why, Bert, wasn’t it yours?”

Bertram admitted that it was not. With a reproachful glance for Bertram, she extended the Cerberus vial to Trenmore. Trenmore reached for it and took it in his hand. In the flash of an eye the space before him was empty. Miss Skidoo had vanished more abruptly than he had himself disappeared, upon his first experience with the dust!

With a startled yell, Terence leaped to his feet and flung the Cerberus across the room. His feelings were shared by all present, save the old collector, who put up a thin, protesting hand.

“Now, don’t—I beg of you, don’t become excited! Mr. Trenmore, my nerves are not in shape to stand this sort of thing. There is no harm done—unless the beautiful little curio is broken, which would be a pity. Tell me, did that violently costumed young lady come here from—well, from the place you have been in since this morning?”

“She did that!”

“Then she has simply returned there,” announced the collector and he settled placidly back in his chair.

But Bertram, who had been stricken temporarily dumb and paralyzed by the abrupt vanishment of his beloved “kid,” gave vent to one anguished cry of grief and rage. Springing upon Drayton, he wrenched from him the newspaper packet.

“What the deuce are you doing?” exclaimed the lawyer.

“You lemme alone!” panted the burglar, backing away. “I want a dose of this dust, that’s what. I’m goin’ after Skidoo, I am!”

“You are not!”

Trenmore pounced on him and recovered the dangerous package. “You poor little maniac,” he said. “Do you think that I rang the Red Bell in that temple for nothing? Don’t you realize that the place where we were isn’t anywhere now, wherever it was before?”

A moment the burglar stood cogitating this puzzling statement, his face the picture of woe. Then he sank slowly into a chair and dropped his head in his hands.

“The brightest kid!” he muttered despairingly. “The best kid and now she’s nothing! Hell—beg pardon, lady, but this’s fierce! I don’t care what happens now!”

They all sincerely pitied him. As, however, there is no known remedy for the loss of a sweetheart who has melted into the circumambient atmosphere, and as he repulsed their sympathy with almost savage impatience, they once more turned their attention to the gray-haired collector.

Trenmore began by asking his name.

The old fellow fumbled in his pockets a moment. “I find I have left my card case,” he said, “but I am Phineas Dodd Scarboro. By profession I am an oculist. I am willing to tell you the history and nature of that dust. In order that I may do so intelligently, however, I must ask that you first relate your own experience with it.”

There seemed nothing unreasonable in this request. Beginning with the first uncapping of the vial, they unfolded their remarkable narrative. Long before that tale was done, Martin had announced supper. The collector adjourned with them to the dining room. Bertram, however, declined, saying that he had no appetite and preferred to stay where he was. So he was left alone, hunched over in his chair, a figure of sorrow inconsolable. Trenmore took the precaution of bringing the packet of dust into the dining room.

“And so,” concluded Trenmore over the coffee cups, “we got back to our own day again, and a very good job it was. I’d sooner put up with any hardships of our own time, than live out my life in the year 2118!”

Phineas Scarboro sniffed scornfully at Terry’s last remark.

“The year fiddlesticks!” he exclaimed impatiently. “You might, if you had used that powder intelligently, have reached a plane where the vibration was so rapid that a year there was the equivalent of one day here. That, however, is the only form of trick you could play with time. To talk of time as a dimension through which one might travel is the merest nonsense. Time is not a dimension. It is a sequence, or rather a comparative sequence, of vibrations.”

Trenmore threw up his hand. “Man, man, don’t confuse us that way; we’ll be worse off than we are now!”

“The sun rose and set at least twice while we were there,” said Drayton.

“And if it was not the year 2118, then what was it and where were we?” This from Viola.

Scarboro placed his fingers together, tip to tip. He contemplated them for a moment without replying.

“Perhaps,” he said at last, “I had best begin where your adventures began—with the Dust of Purgatory. In my freshman year at Harvard I made the acquaintance of a young man destined to influence my life in a very remarkable manner. His name was Andrew Power. You appear startled. That was the name, was it not, which you, Mr. Drayton, encountered in the temple library as the man who had carried out the scheme for state isolation? The appearance of that name is one of those inexplicable circumstances which in my own investigations have often obtruded themselves.

“Andrew Power, then, was a young man of very unusual abilities. He was, in fact, a theorist along lines so novel that he became persona non grata to more than one member of the faculty. In those days they were convinced that science had achieved her ultimate victories. Any one who pointed out new worlds to conquer was a heretic or worse. Finding no sympathy in his instructors, Power brought his theories to me and to Thaddeus B. Crane, who was then my roommate. The three of us struck up one of those intense friendships of boyhood. On many a night we argued and wrangled into the small hours over subjects of whose very existence Thaddeus and I would scarcely have been aware, save for Andrew Power.

“His chief interest lay in the fields of the occult, which he approached from the angle of sheer materialism. To expound his theories even in brief would require more time than you, I am sure, would care to expend in listening. Enough that he was deeply interested in the Eastern religions—he was born in India, by the way, and had studied under some of their greatest pundits—and contended that their mysticism was based on scientifically demonstrable facts.”

In spite of himself, Trenmore yawned. Was the man never going to reach the dust?

“In his own words,” continued Scarboro, “Power believed it possible to ‘reduce psychic experiences to a material basis! You smile”—They hadn’t—“but Andrew Power, whom we secretly considered a mad theorist, proved himself far more practical than Crane and I, who merely talked. The faculty objected to experiments along any line not in the regular curriculum. Power, however, had set up for himself a small private laboratory.

“One night he came to us ablaze with excitement. In his hand was a glass specimen jar, half filled with this gray, powdery stuff. ‘Fellows,’ he said, ‘I’ve done the thing at last. I’ve precipitated RI.’ Though we hadn’t the vaguest idea what he was talking about, we managed not to give ourselves away. We led him on to explanation. This powder, he said, was of a substance more magical than the fabled philosopher’s stone, which could at most but transmute one element into another. Taken into the system of a living creature this substance so altered the vibrations of the electrons—he called them atomic corpuscles, but electrons is the modern term—of not only the body but of any other matter within the immediate radius of its magnetism that these vibrations were modified to function on an entirely different plane from this with which we are familiar from birth. This other world, or rather these worlds, lie within or in the same place as our own. The old axiom, that two bodies cannot exist simultaneously in the same place, was, according to Power, an axiom no more. Two bodies, a hundred bodies, could by inter-vibration exist in precisely the same place. And therein lay the explanation of every materialization, every ‘miracle,’ every ‘super-natural’ wonder since the world began. Mediums, clairvoyants, prophets, and yogis, all had their occasional spiritual glimpses of these hidden planes or worlds. What Power desired—what he had accomplished—was the actual physical entry.

“Needless to say, we scoffed. We angered Power to the point where he was ready to actually demonstrate. Later we learned from his notes that he had only translated an unlucky cat or so to these secret realms, and was personally inexperienced. Driven, however, by our laughter, Power took about ten grains of the powder and placed it on his tongue. He disappeared. From that day to this no one, not even I, who have many times gone the same road and returned, has ever seen Andrew Power.

“We two escaped arrest only because our unfortunate friend had not been seen coming to our rooms that night. There was a great fuss made over his supposed murder, and the country for miles around was searched for days. Thaddeus and I, two frightened boys, kept still. The first day or so we had access to his laboratory, where we read his notes in the hope of being able to reverse his disastrous experiment on himself. Then everything was locked up and later his effects were shipped to his only living relative, an uncle in Delhi. But the formula for the dust was not among them. That, before my eyes and in the face of my frantic protest, Thaddeus Crane had destroyed.

“He would have destroyed the powder also, had I not persuaded him that it was our moral duty to hold it in case of Andrew Power’s return. He was always a bit afraid of Andrew. In the face of that contingency he suddenly saw his arbitrary act with the formula in its true light. So Crane and I divided the powder between us, promising each other to hold it in case Power should ever return.

“But Crane had had enough and more than enough. He would never afterward discuss even with me the theories which had cost human............