It was six o’clock when Nick Carter returned to the Wilton House. Daylight was deepening to dusk. The last editions of the local newspapers were out, and the shrill voices of juvenile venders could be heard from all directions. The detective glanced at the papers, which in headline luridness proclaimed:

“Leading Lawyer Suspected in Todd Murder! Frank Paulding Arrested! Chief Gleason Sure of His Man!”

Nick Carter smiled faintly, but with a more threatening gleam and glitter deep down in his eyes, when these varied cries of the newsboys reached his ears. He bought a paper from one, thrusting it into his pocket, and entered the hotel.

“Gleason has made good, all right,” he muttered while seeking the elevator. “That will make it easier for me, as well as all this, which is precisely what I expected. But it’s up to me, by Jove! and must be done quickly, or good night to my reputation.”

He referred to what he had overheard while threading his way through the unusual throng in the hotel office. There was much excitement and only one matter under discussion—the alleged murder, the mystery shrouding it, the strange death of the victim, and divers opinions regarding the suspected man.

The detective went up to his suite, where, as he expected, he found Chick and Patsy waiting for him, the former eager to report what he had learned from Nellie Fielding. It took him only a few moments, and apparently, as Chick had reasoned, it seemed only to deepen the mystery. It brought a look of grim satisfaction, however, to the face of the listening detective.

“I cannot see that it sheds any light on the case,” Chick added perplexedly.

“It does, Chick, nevertheless,” Carter said confidently.

“Does it dovetail with something you have discovered?”

“You may judge for yourself. I’ll tell you what I saw and learned during my call on Doctor Devoll.”

He proceeded to do so, but the look of perplexity still lingered on Chick’s face, and Patsy appeared dubiously puzzled.

“It is somewhat significant, if you are right, chief, that both Doctor Devoll and his man lied to you,” Chick said thoughtfully. “But I don’t see that what the physician said to you or the position he took cuts any ice.”

“You don’t, eh?” returned Carter, smiling grimly. “It cuts quite thick ice, Chick.”

“Why so? I don’t get you.”

“Gee whiz, chief, nor do I,” put in Patsy. “What do you mean? Come across with it.”

“First, a word about the girl, Nellie Fielding, and what befell her,” said Carter. “It probably is precisely what befell the others, and all were victims of the same crook and his assistant. Just what game he was playing and with what object remains to be learned.”

“But——”

“Wait a bit!” Carter cut in. “You’ll get me presently. Nellie Fielding evidently told you the truth. The mysterious bag was deftly slipped into her hand. She did what the others did, when she could discover no owner for it. She kept it until well away from the crowd, then opened it to see what it contained. As you have inferred, Chick, something in the bag, probably that with which the handkerchief was saturated, immediately overcame her. A very powerful and mysterious gas may have been liberated from the bag, and it naturally would have been inhaled by the girl when she peered into it.”

“That seemed to me the most plausible theory,” said Chick.

“It has become rather more than a theory,” Carter replied. “I now am almost sure of it.”

“For other reasons?”

“Yes. To continue, it is safe to assume that the girl was constantly watched. The moment she lost herself, for she certainly lost consciousness to some extent, at least, she was taken away by two men and placed on the seat in the hospital grounds, then wholly unconscious, where Policeman Donovan found her.”

“Barclay was right, then,” said Chick. “That was the cab seen by the artist.”

“Undoubtedly.”

“But why was the girl taken into the hospital grounds?”

“That’s one point,” said Carter. “So that, when discovered, she would surely be taken into the hospital—where Doctor Devoll would be the one to treat her.”

“You think——”

“One moment. Don’t force me ahead of my story. These circumstances require careful and thorough analysis.”

“Go ahead, then.”

“Bear in mind that Doctor Devoll treated all four of these cases. He treated them successfully. They did not appear to baffle him, or even mystify him, I suspect. Bear in mind, too, that he did not detain the girls, did not question them closely, or seek to learn their names, even, with the exception of Nellie Fielding. Remember, too, that the mysterious leather bag, which Sergeant Brady knows was taken into the wardroom, could not be found. Take it from me—Doctor Devoll was the one who got away with it.”

“By Jove! all that does appear deucedly suspicious,” Chick now declared. “It may explain, too, Devoll’s attitude this afternoon.”

“Exactly.”

“Exactly, chief, is right,” cried Patsy. “Gee! things are beginning to brighten up.”

“Let’s go a step farther,” Carter continued. “All of the mysterious robberies and holdups during the past three months, which we were called here to investigate, were of a very similar character, and all bore a striking likeness to what befell Nellie Fielding. The victims invariably were found unconscious after the crime, though afterward were quite easily restored, and all told the same story—that of being confronted by a person who, in some mysterious way, caused them to immediately lose consciousness and then deliberately robbed them.”

“You think all of these cases, then, were the work of the same gang of crooks.”

“That is precisely what I think,” Carter said more forcibly. “I am convinced of it by their similarity and the mysterious means employed, which show plainly that the knave back of the whole business is an exceedingly capable and well-informed rascal. He must be an expert in drugs, or have discovered some chemical compound the quality and effect of which are not known by other physicians and scientists.”

“Do you suspect that Doctor Devoll is the criminal?” Chick inquired.

“I do not like his looks, his conduct in these cases, or the position he took when I questioned him.”

“But it seems really improbable that a man of his prominence and profession would be engaged in such knavery,” Chick argued.

“That’s what every one would say, and it would be deucedly difficult to convince them of his guilt,” Carter replied. “That could be done only by producing positive evidence of it.”

“Very true.”

“It may be equally difficult to find that evidence,” Carter added. “It must be found, nevertheless, assuming that I am right. In no other way can we make good.”

“True again,” Chick admitted.

“I was very careful, therefore, not to betray that I suspected him. I pretended to swallow all that he handed out, and let it go at that. One word more, now, and I will have covered all of the ground. That relates to the Todd murder.”

“What about it?”

“The mystery is as to how and with what means it was committed. You know what the autopsy revealed——”

“Next to nothing,” put in Patsy.

“That’s the very point,” said Nick. “Chemical tests may reveal the presence of poison. Doctor Marvin thinks, however, and I am of the same opinion, that Todd was killed with some kind of poisonous gas.”

“Great Scott! that seems next to impossible,” Chick declared. “Consider the time, the public place, and all of the circumstances. Todd was telephoned to come to the Waldmere Chambers and wait in the corridor. It was done at a moment’s notice, so to speak, with a view to incriminating Frank Paulding, if your suspicions are correct. How in thunder could a poisonous gas be administered to a man under such conditions?”

“Gee whiz! it does look like an utter impossibility, chief,” said Patsy.

“Or the work of an exceedingly bold and accomplished crook, the same crook who committed these other mysterious crimes,” Carter insisted. “Their similarity convinces me, as I have said, that all were the work of the same man and same gang.”

“That much does seem probable,” Chick allowed. “There is no getting around it.”

“And it’s up to us to get after them and find the evidence needed to identify and convict them,” Carter said flatly. “Now, Patsy, what have you learned? Is there any man who might properly term himself Todd’s running mate? That’s what the telephone girl heard.”

“I have not been able to find one, chief,” Patsy reported. “There seems to be no man with whom he was specially friendly.”

“Nor any tenant in the Waldmere Chambers whom he was in the habit of visiting?”

“Not that I could learn,” Patsy again replied in the negative. “I questioned the janitor and several others. Not one of them had ever seen Todd in the building. So far as I could learn, chief, he never visited the Waldmere Chambers.”

“All the more reason, then, for suspecting that he was lured there that day only to be killed.”

“But I have learned one fact, chief,” Patsy added.

“What is that?”

“Todd had a suite here in the Wilton House for the past two years. About a month ago, however, he changed his quarters to the Studley. That is an apartment house in Dale Street. His suite is on the second floor.”

“He may have had some secret motive for the change,” Carter said thoughtfully. “The hotel may have been too public a place for something in which he was secretly engaged. We must look into that. No investigation in his apartments has yet been made.”

“We had better make one, then,” Chick suggested.

“I was coming to that. You go there this evening and see what you can find. Search for letters, papers, or anything that might shed a ray of light on the case.”

“Leave it to me,” Chick nodded. “I’ll go through his suite with a fine-tooth comb.”

“Accomplish it secretly, however, if possible,” Carter quickly directed. “I don’t want our doings and designs suspected by the miscreants back of this knavery. I want to keep them in the dark as long as possible.”

“Leave it to me. I’ll turn the trick without being seen,” Chick predicted confidently.

“In the meantime, Patsy, you go at once to the Osgood Hospital and watch for any move by Doctor Devoll,” said Nick, abruptly turning to him. “My visit may, if my suspicions are warranted, alarm him into taking steps that would clinch them. Shadow him, if he goes out, and watch him constantly.”

“Enough said, chief,” cried Patsy, springing up to get his hat. “He’ll be a good one, indeed, if he gets by me with a move of any kind. I’ll soon have my lamps on him.”

Patsy did not wait for an answer. He was out and away almost as soon as the last was said.