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.