“Holmes!” he cried.

“Why, Gregson!” said my companion as he shook hands with the Scotland Yard detective. “Journeys end with lovers’ meetings. What brings you here?”

“The same reasons that bring you, I expect,” said Gregson. “How you got on to it I can’t imagine.”

“Different threads, but leading up to the same tangle. I’ve been taking the signals.”

“Signals?”

“Yes, from that window. They broke off in the middle. We came over to see the reason. But since it is safe in your hands I see no object in continuing the business.”

“Wait a bit!” cried Gregson eagerly. “I’ll do you this justice, Mr. Holmes, that I was never in a case yet that I didn’t feel stronger for having you on my side. There’s only the one exit to these flats, so we have him safe.”

“Who is he?”

“Well, well, we score over you for once, Mr. Holmes. You must give us best this time.” He struck his stick sharply upon the ground, on which a cabman, his whip in his hand, sauntered over from a four-wheeler which stood on the far side of the street. “May I introduce you to Mr. Sherlock Holmes?” he said to the cabman. “This is Mr. Leverton, of Pinkerton’s American Agency.”

“The hero of the Long Island cave mystery?” said Holmes. “Sir, I am pleased to meet you.”

The American, a quiet, businesslike young man, with a clean-shaven, hatchet face, flushed up at the words of commendation. “I am on the trail of my life now, Mr. Holmes,” said he. “If I can get Gorgiano- -”

“What! Gorgiano of the Red Circle?”

“Oh, he has a European fame, has he? Well, we’ve learned all about him in America. We know he is at the bottom of fifty murders, and yet we have nothing positive we can take him on. I tracked him over from New York, and I’ve been close to him for a week in London, waiting some excuse to get my hand on his collar. Mr. Gregson and I ran him to ground in that big tenement house, and there’s only the one door, so he can’t slip us. There’s three folk come out since he went in, but I’ll swear he wasn’t one of them.”

“Mr. Holmes talks of signals,” said Gregson. “I expect, as usual, he knows a good deal that we don’t.”

In a few clear words Holmes explained the situation as it had appeared to us. The American struck his hands together with vexation.

“He’s on to us!” he cried.

“Why do you think so?”

“Well, it figures out that way, does it not? Here he is, sending out messages to an accomplice - there are several of his gang in London. Then suddenly, just as by your own account he was telling them that there was danger, he broke short off. What could it mean except that from the window he had suddenly either caught sight of us in the street, or in some way come to understand how close the danger was, and that he must act right away if he was to avoid it? What do you suggest, Mr. Holmes?”

“That we go up at once and see for ourselves.”

“But we have no warrant for his arrest.”

“He is in unoccupied premises under suspicious circumstances,” said Gregson. “That is good enough for the moment. When we have him by the heels we can see if New York can’t help us to keep him. I’ll take the responsibility of arresting him now.”

Our official detectives may blunder in the matter of intelligence, but never in that of courage. Gregson climbed the stair to arrest this desperate murderer with the same absolutely quiet and businesslike bearing with which he would have ascended the official staircase of Scotland Yard. The Pinkerton man had tried to push past him, but Gregson had firmly elbowed him back. London dangers were the privilege of the London force.