“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 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.