“I believe you have hit it.”

“Not a doubt of it. It is a very urgent message, thrice repeated to make it more so. But beware of what? Wait a bit; he is coming to the window once more.”

Again we saw the dim silhouette of a crouching man and the whisk of the small flame across the window as the signals were renewed. They came more rapidly than before — so rapid that it was hard to follow them.

“PERICOLO pericolo — eh, what’s that, Watson? ‘Danger,’ isn’t it? Yes, by Jove, it’s a danger signal. There he goes again! PERI. Halloa, what on earth —”

The light had suddenly gone out, the glimmering square of window had disappeared, and the third floor formed a dark band round the lofty building, with its tiers of shining casements. That last warning cry had been suddenly cut short. How, and by whom? The same thought occurred on the instant to us both. Holmes sprang up from where he crouched by the window.

“This is serious, Watson,” he cried. “There is some devilry going forward! Why should such a message stop in such a way? I should put Scotland Yard in touch with this business — and yet, it is too pressing for us to leave.”

“Shall I go for the police?”

“We must define the situation a little more clearly. It may bear some more innocent interpretation. Come. Watson, let us go across ourselves and see what we can make of it.”

—

As we walked rapidly down Howe Street I glanced back at the building which we had left. There, dimly outlined at the top window, I could see the shadow of a head, a woman’s head, gazing tensely, rigidly, out into the night, waiting with breathless suspense for the renewal of that interrupted message. At the doorway of the Howe Street flats a man, muffled in a cravat and greatcoat, was leaning against the railing. He started as the hall-light fell upon our faces.

“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.”