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."