Saul Arthur Mann came back to England full of his news, and found Frank at the little Jermyn Street hotel where he had installed himself, and Frank listened without interruption to the story of the letter.

"Of course," the little fellow went on, "I went straight over to Montreux. The note heading was not on the paper, but I had no difficulty, by comparing the qualities of papers used at the various hotels, in discovering that it was written from the Palace. The head waiter knew this Rex Holland, who had been a frequent visitor, had always tipped very liberally, and lived in something like style. He could not describe his patron, except that he was a young man with a very languid manner who had arrived the previous morning from Holland and had immediately inquired for Frank Merrill."

"From Holland! Are you sure it was the morning? I have a particular reason for asking," asked Frank quickly.

"No, it was not in the morning, now you mention it. It was in the evening. He left again the following morning by the northern train."

"How did he find my address?" asked Frank.

"Obviously from the visitors' list. The waiter on duty in the writing room remembered having seen him consulting the newspaper. Now, my boy, you have to be perfectly candid with me. What do you know about Rex Holland?"

Frank opened his case, took out a cigarette, and lit it before he replied.

"I know what everybody knows about him," he said, with a hint of bitterness in his voice, "and something which nobody knows but me."

"But, my dear fellow," said Saul Arthur Mann, laying his hand on the other's shoulder, "surely you realize how important it is for you that you should tell me all you know."

Frank shook his head.

"The time is not come," he said, and he would make no further statement.

But on another matter he was emphatic.

"By heaven, Mann, I am not going to stand by and see May ruin her life. There's something sinister in this influence which Jasper is exercising over her. You have seen it for yourself."

Saul Arthur nodded.

"I can't understand what it is," he confessed. "Of course Jasper is not a bad-looking fellow. He has perfect manners and is a charming companion. You don't think—"

"That he is winning on his merits?" Frank shook his head. "No, indeed, I do not. It is difficult for me to discuss my private affairs, and you know how reluctant I am to do so, but you are also aware of what I think of May. I was hoping that we should go back to the place where we left off, and, although she is kindness itself, this girl who is more to me than anything or anybody in the world, and who was prepared to marry me, and would have married me but for Jasper's machinations, was almost cold."

He was walking up and down the room, and now halted in his stride and spread out his arms despairingly.

"What am I to do? I cannot lose her. I cannot!"

There was a fierceness in his tone which revealed the depth of his feeling, and Saul Arthur Mann understood.

"I think it is too soon to say you have lost her, Frank," he said.

He had conceived a genuine liking for Frank Merrill, and the period of tribulation through which the young man had passed had heightened the respect in which he held him.

"We shall see light in dark places before we go much farther," he said. "There is something behind this crime, Frank, which I don't understand, but which I am certain is no mystery to you. I am sure that you are shielding somebody, for what reason I am not in a position to tell, but I will get to the bottom of it."

No event in the interesting life of this little man, who had spent his years in the accumulation of facts, had so distressed and piqued him as the murder of John Minute. The case had ended where the trial had left it.

Crawley, who might have offered a new aspect to the tragedy, had disappeared as completely as though the earth had swallowed him. The most strenuous efforts which the official police had made, added to the investigations which Saul Arthur Mann had conducted independently, had failed to trace the fugitive ex-sergeant of police. Obviously, he was not to be confounded with Rex Holland. He was a distinct personality working possibly in collusion, but there the association ended.

It had occurred to the investigator that possibly Crawley had accompanied Rex Holland in his flight, but the most careful inquiries which he had pursued at Montreux were fruitless in this respect as in all others.

To add to his bewilderment, investigations nearer at home were constantly bringing him across the track of Frank Merrill. It was as though fate had conspired to show the boy in the blackest light. Frank had been acting as secretary to his uncle, and then Jasper Cole had suddenly appeared upon the scene from nowhere in particular. The suggestion had been made somewhat vaguely that he had come from "abroad," and it was certain that he arrived as a result of long negotiations which John Minute himself had conducted. They were negotiations which involved months of correspondence, no letter of which either from one or the other had Frank seen.

While the trial was pending, the little man collected quite a volume of information, both from Frank and the girl, but nothing had been quite as inexplicable as this intrusion of Jasper Cole upon the scene, or the extraordinary mystery which John Minute had made of his engagement.

He had written and posted all the letters to Jasper himself, and had apparently received the replies, which he had burned, at some other address of which Frank was ignorant.

Jasper had come, and then one day there had been a quarrel, not between the two young men, but between Frank and his uncle. It was a singularly bitter quarrel, and again Frank refused to discuss the cause. He left the impression upon Saul Arthur's mind that he had to some extent been responsible. And here was another fact which puzzled "The Man Who Knew." Sergeant Smith, as he was then, had been to some extent responsible. It was Frank who had introduced the sergeant to Eastbourne and brought him to his uncle. But this was only one aspect of the mystery. There were others as obscure.

Saul Arthur Mann went back to his bureau, and for the twentieth time gathered the considerable dossiers he had accumulated relating to the case and to the characters, and went through them systematically and carefully.

He left his office near midnight, but at nine o'clock the next morning was on his way to Eastbourne. Constable Wiseman was, by good fortune, enjoying a day's holiday, and was at work in his kitchen garden when Mr. Mann's car pulled up before the cottage. Wiseman received his visitor importantly, for, though the constable's prestige was regarded in official circles as having diminished as a result of the trial, it was felt by the villagers that their policeman, if he had not solved the mystery of John Minute's death, had at least gone a long way to its solution.

In the spotless room which was half kitchen and half sitting room, with its red-tiled floor covered by bright matting, Mrs. Wiseman produced a well-dusted Windsor chair, which she placed at Saul Arthur Mann's disposal before she politely vanished. In a very few words the investigator stated his errand, and Constable Wiseman listened in noncommittal silence. When his visitor had finished, he shook his head.

"The only thing about the sergeant I know," he said, "I have already told the chief constable who sat in that very chair," he explained. "He was always a bit of a mystery—the sergeant, I mean. When he was 'tanked,' if I may use the expression, he would tell you stories by the hour, but when he was sober you couldn't get a word out of him. His daughter only lived with him for about a fortnight."

"His daughter!" said Mr. Mann quickly.

"He had a daughter, as I've already notified my superiors," said Constable Wiseman gravely. "Rather a pretty girl. I never saw much of her, but she was in Eastbourne off and on for about a fortnight after the sergeant came. Funny thing, I happen to know the day he arrived, because the wheel of his fly came off on my beat, and I noticed the circumstances according to law and reported the same. I don't even know if she was living with him. He had a cottage down at Birlham Gap, and that is where I saw her. Yes, she was a pretty girl," he said reminiscently; "one of the slim and slender kind, very dark and with a complexion like milk. But they never found her," he said.

Again Mr. Mann interrupted.

"You mean the police?"

Constable Wiseman shook his head.

"Oh, no," he said; "they've been looking for her for years; long before Mr. Minute was killed."

"Who are 'they'?"

"Well, several people," said the constable slowly. "I happen to know that Mr. Cole wanted to find out where she was. But then he didn't start searching until weeks after she disappeared. It is very rum," mused Constable Wiseman, "the way Mr. Cole went about it. He didn't come straight to us and ask our assistance, but he had a lot of private detectives nosing round Eastbourne; one of 'em happened to be a cousin of my wife's. So we got to know about it. Cole spent a lot of money trying to trace her, and so did Mr. Minute."

Saul Arthur Mann saw a faint gleam of daylight.

"Mr. Minute, too?" he asked. "Was he working with Mr. Cole?"

"So far as I can find out, they were both working independent of the other—Mr. Cole and Mr. Minute," explained Mr. Wiseman. "It is what I call a mystery within a mystery, and it has never been properly cleared up. I thought something was coming out about it at the trial, but you know what a mess the lawyers made of it."

It was Constable Wiseman's firm conviction that Frank Merrill had escaped through the incompetence of the crown authorities, and there were moments in his domestic circle when he was bitter and even insubordinate on the subject.

"You still think Mr. Merrill was guilty?" asked Saul Arthur Mann as he took his leave of the other.

"I am as sure of it as I am that I am standing here," said the constable, not without a certain pride in the consistency of his view. "Didn't I go into the room? Wasn't he there with the deceased? Wasn't his revolver found? Hadn't there been some jiggery-pokery with his books in London?"

Saul Arthur Mann smiled.

"There are some of us who think differently, Constable," he said, shaking hands with the implacable officer of the law.

He brought back to London a few new facts to be added to his record of Sergeant Crawley, alias Smith, and on these he went painstakingly to work.

As has been already explained, Saul Arthur Mann had a particularly useful relationship with Scotland Yard, and fortunately, about that time, he was on the most excellent terms with official police headquarters, for he had been able to assist them in running to earth one of the most powerful blackmailing gangs that had ever operated in Europe. His files had been drawn upon to such good purpose that the police had secured convictions against the seventeen members of the gang who were in England.

He sought an interview with the chief commissioner, and that same night, accompanied by a small army of detectives, he made a systematic search of Silvers Rents. The house into which Jasper Cole had been seen to enter was again raided, and again without result. The house was empty save for one room, a big room which was simply furnished with a truckle-bed, a table, a chair, a lamp, and a strip of carpet. There were four rooms—two upstairs, which were never used, and two on the ground floor.

At the end of a passage was a kitchen, which also was empty, save for a length of bamboo ladder. From the kitchen a bolted door led on to a tiny square of yard which was separated by three walls from yards of similar dimensions to left and right and to the back of the premises. At the back of Silvers Rents was Royston Court, which was another cul-de-sac, running parallel with Silvers Rents.

Mr. Mann returned to the house, and again searched the upstairs rooms, looking particularly for a trapdoor, for the bamboo ladder suggested some such exit. This time, however, he completely failed. Jasper Cole, he found, had made only one visit to the house since John Minute's death.

It is a curious fact, as showing the localizing of interest, that Silvers Rents knew nothing of what had occurred almost at its doors, and, though it had at its finger tips all the gossip of the docks and the Thames Iron Works, it was profoundly ignorant of what was common property in Royston Court. It is even more remarkable that Saul Arthur Mann, with his squadron of detectives, should have confined their investigations to Silvers Rents.

The investigator was baffled and disappointed, but by the oddest of chances he was to pick up yet another thread of the Minute mystery, a thread which, however, was to lead him into an ever-deeper maze than that which he had already and so unsuccessfully attempted to penetrate.

Three days after his search of Silvers Rents, business took Mr. Mann to Camden Town. To be exact, he had gone at the request of the police to Holloway Jail to see a prisoner who had turned state's evidence on a matter in which the police and Mr. Mann were equally interested. Very foolishly he had dismissed his taxi, and when he emerged from the doors there was no conveyance in sight. He decided, rather than take the trams which would have carried him to King's Cross, to walk, and, since he hated main roads, he had taken a short cut, which, as he knew, would lead him into the Hampstead Road.

Thus he found himself in Flowerton Road, a thoroughfare of respectable detached houses occupied by the superior industrial type. He was striding along, swinging his umbrella and humming, as was his wont, an unmusical rendering of a popular tune, when his attention was attracted to a sight which took his breath away and brought him to a halt.

It was half past five, and dull, but his eyesight was excellent, and it was impossible for him to make a mistake. The houses of Flowerton Road stand back and are separated from the sidewalk by diminutive gardens. The front doors are approached by six or seven steps, and it was on the top of one of these flights in front of an open door that the scene was enacted which brought Mr. Mann to a standstill.

The characters were a young man and a girl. The girl was extremely pretty and very pale. The man was the exact double of Frank Merrill. He was dressed in a rough tweed suit, and wore a soft felt hat with a fairly wide brim. But it was not the appearance of this remarkable apparition which startled the investigator. It was the attitude of the two people. The girl was evidently pleading with her companion. Saul Arthur Mann was too far away to hear what she said, but he saw the young man shake himself loose from the girl. She again grasped his arm and raised her face imploringly.

Mr. Mann gasped, for he saw the young man's hand come up and strike her back into the house. Then he caught hold of the door and banged it savagely, walked down the stairs, and, turning, hurried away.

The investigator stood as though he were rooted to the spot, and before he could recover himself the fellow had turned the corner of the road and was out of sight. Saul Arthur Mann took off his hat and wiped his forehead. All his initiative was for the moment paralyzed. He walked slowly up to the gate and hesitated. What excuse could he have for calling? If this were Frank, assuredly his own views were all wrong, and the mystery was a greater mystery still.

His energies began to reawaken. He took a note of the number of the house, and hurried off after the young man. When he turned the corner his quarry had vanished. He hurried to the next corner, but without overtaking the object of his pursuit. Fortunately, at this moment, he found an empty taxicab and hailed it.

"Grimm's Hotel, Jermyn Street," he directed.

At least he could satisfy his mind upon one point.