T. B. Smith sat alone in his office in Scotland Yard. Outside, the Embankment, the river, even the bulk of the Houses of Parliament were blotted out by the dense fog. For two days London had lain under the pall, and if the weather experts might be relied upon, yet another two days of fog was to be expected.

The cheery room, with its polished oak panelling and the chaste elegance of its electroliers, offered every inducement to a lover of comfort to linger. The fire glowed bright and red in the tiled fireplace, a silver clock on the mantelpiece ticked musically, and at his hand was a white-covered tray with a tiny silver teapot, and the paraphernalia necessary for preparing his meal—that strange tea-supper which was one of T. B. Smith's eccentricities.

He glanced at the clock; the hands pointed to twenty-five minutes past one.

He pressed a little button let into the side of the desk, and a few seconds later there was a gentle tap at the door, and a helmetless constable appeared.

"Go to the record room and get me"—he consulted a slip of paper on the desk—"Number G 7941."

The man withdrew noiselessly, and T. B. Smith poured out a cup of tea for himself.

There was a thoughtful line on his broad forehead, a look of unaccustomed worry on the handsome face, tanned with the suns of Southern France. He had come back from his holiday to a task which required the genius of a superman. He had to establish the identity of the greatest swindler of modern times, Montague Fallock. And now another reason existed for his search. To Montague Fallock, or his agent, must be ascribed the death of two men found in Brakely Square the night before.

No man had seen Montague; there was no photograph to assist the army of detectives who were seeking him. His agents had been arrested and interrogated, but they were but the agents of agents. The man himself was invisible. He stood behind a steel network of banks and lawyers and anonymities, unreachable.

The constable returned, bearing under his arm a little black leather envelope, and, depositing it on the desk of the Assistant Commissioner, withdrew.

T. B. opened the envelope and removed three neat packages tied with red tape. He unfastened one of these and laid three cards before him. They were three photographic enlargements of a finger print. It did not need the eye of an expert to see they were of the same finger, though it was obvious that they had been made under different circumstances.

T. B. compared them with a smaller photograph he had taken from his pocket. Yes, there was no doubt about it. The four pictures, secured by a delicate process from the almost invisible print on the latest letter of the blackmailer, proved beyond any doubt the identity of Lady Dex's correspondent.

He rang the bell again and the constable appeared in the doorway.

"Is Mr. Ela in his office?"

"Yes, sir. He's been taking information about that Dock case."

"Dock case? Oh yes, I remember; two men were caught rifling the Customs store; they shot a dock constable and got away."

"They both got away, sir," said the man, "but one was shot by the constable's mate; they found his blood on the pavement outside where their motor-car was waiting."

T. B. nodded.

"Ask Mr. Ela to come in when he is through," he said.

Mr. Ela was evidently "through," for almost immediately after the message had gone, the long, melancholy face of the superintendent appeared in the doorway.

"Come in, Ela," smiled T. B.; "tell me all your troubles."

"My main trouble," replied Ela, as he sank wearily into the padded chair, "is to induce eyewitnesses to agree as to details; there is absolutely no clue as to the identity of the robbers, and nearly murderers. The number of the car was a spurious one, and was not traced beyond Limehouse. I am up against a blank wall. The only fact I have to go upon is the very certain fact that one of the robbers was either wounded or killed and carried to the car by his friend, and that his body will have to turn up somewhere or other—then we may have something to go on."

"If it should prove to be that of my friend Montague Fallock," said T. B. humorously, "I shall be greatly relieved. What were your thieves after—bullion?"

"Hardly! No, they seem to be fairly prosaic pilferers. They engaged in going through a few trunks—part of the personal baggage of the Mandavia which arrived from Coast ports on the day previous. The baggage was just heavy truck; the sort of thing that a passenger leaves in the docks for a day or two till he has arranged for their carriage. The trunks disturbed, included one of the First Secretary to a High Commissioner in Congoland, a dress basket of a Mrs. Somebody-or-other whose name I forget—she is the wife of a Commissioner—and a small box belonging to Dr. Goldworthy, who has just come back from the Congo where he has been investigating sleeping sickness."

"Doesn't sound thrilling," said T. B. thoughtfully; "but why do swagger criminals come in their motor-cars with their pistols and masks—they were masked if I remember the printed account aright?" Ela nodded. "Why do they come on so prosaic an errand?"

"Tell me," said Ela, laconically, then, "What is your trouble?"

"Montague," said the other, with a grim smile, "Montague Fallock, Esquire. He has been demanding a modest ten thousand pounds from Lady Constance Dex—Lady Constance being a sister of the Hon. and Rev. Harry Dex, Vicar of Great Bradley. The usual threat—exposure of an old love affair.

"Dex is a large, bland aristocrat under the thumb of his sister; the lady, a masterful woman, still beautiful; the indiscretion partly atoned by the death of the man. He died in Africa. Those are the circumstances that count. The brother knows, but our friend Montague will have it that the world should know. He threatens to murder, if necessary, should she betray his demands to the police. This is not the first time he has uttered this threat. Farrington, the millionaire, was the last man, and curiously, a friend of Lady Dex."

"It's weird—the whole business," mused Ela. "The two men you found in the square didn't help you?"

T. B., pacing the apartment with his hand in his pocket, shook his head.

"Ferreira de Coasta was one, and Henri Sans the other. Both men undoubtedly in the employ of Montague, at some time or other. The former was a well-educated man, who may have acted as intermediary. He was an architect who recently got into trouble in Paris over money matters. Sans was a courier agent, a more or less trusted messenger. There was nothing on either body to lead me to Montague Fallock, save this."

He pulled open the drawer of his desk and produced a small silver locket. It was engraved in the ornate style of cheap jewellery and bore a half-obliterated monogram.

He pried open the leaf of the locket with his thumbnail. There was nothing in its interior save a small white disc.

"A little gummed label," explained T. B., "but the inscription is interesting."

Ela held the locket to the light, and read:

"Mor: Cot.
God sav the Keng."

"Immensely patriotic, but unintelligible and illiterate," said T. B., slipping the medallion into his pocket, and locking away the dossier in one of the drawers of his desk.

Ela yawned.

"I'm sorry—I'm rather sleepy. By the way, isn't Great Bradley, about which you were speaking, the home of a romance?"

T. B. nodded with a twinkle in his eye.

"It is the town which shelters the Secret House," he said, as he rose, "but the eccentricities of lovesick Americans, who build houses equally eccentric, are not matters for police investigation. You can share my car on a fog-breaking expedition as far as Chelsea," he added, as he slipped into his overcoat and pulled on his gloves; "we may have the luck to run over Montague."

"You are in the mood for miracles," said Ela, as they were descending the stairs.

"I am in the mood for bed," replied T. B. truthfully. Outside the fog was so thick that the two men hesitated. T. B.'s chauffeur was a wise and patient constable, but felt in his wisdom that patience would be wasted on an attempt to reach Chelsea.

"It's thick all along the road, sir," he said. "I've just 'phoned through to Westminster Police Station, and they say it is madness to attempt to take a car through the fog."

T. B. nodded.

"I'll sleep here," he said. "You'd better bed down somewhere, David, and you, Ela?"

"I'll take a little walk in the park," said the sarcastic Mr. Ela.

T. B. went back to his room, Ela following.

He switched on the light, but stood still in the doorway. In the ten minutes' absence some one had been there. Two drawers of the desk had been forced; the floor was littered with papers flung there hurriedly by the searcher.

T. B. stepped swiftly to the desk—the envelope had gone.

A window was open and the fog was swirling into the room.

"There's blood here," said Mr. Ela. He pointed to the dappled blotting pad.

"Cut his hand on the glass," said T. B. and jerked his head to the broken pane in the window. He peered out through the open casement. A hook ladder, such as American firemen use, was hanging to the parapet. So thick was the fog that it was impossible to see how long the ladder was, but the two men pulled it up with scarcely an effort. It was made of a stout light wood, with short steel brackets affixed at intervals.

"Blood on this too," said Ela, then, to the constable who had come to his ring, he jerked his orders rapidly: "Inspector on duty to surround the office with all the reserve—'phone Cannon Row all men available to circle Scotland Yard, and to take into custody a man with a cut hand—'phone all stations to that effect."

"There's little chance of getting our friend," said T. B. He took up a magnifying glass and examined the stains on the pad.

"Who was he?" asked Ela.

T. B. pointed to the stain.

"Montague," he said, briefly, "and he now knows the very thing I did not wish him to know."

"And that is?"

T. B. did not speak for a moment. He stood looking down at the evidence which the intruder had left behind.

"He knows how much I know," he said, grimly, "but he may also imagine I know more—there are going to be developments."