The man groaned and sank his face in his hands. We waited, but he was silent.

“I can assure you,” said Holmes, “that every essential is already known. We know that you were pressed for money; that you took an impress of the keys which your brother held; and that you entered into a correspondence with Oberstein, who answered your letters through the advertisement columns of the Daily Telegraph. We are aware that you went down to the office in the fog on Monday night, but that you were seen and followed by young Cadogan West, who had probably some previous reason to suspect you. He saw your theft, but could not give the alarm, as it was just possible that you were taking the papers to your brother in London. Leaving all his private concerns, like the good citizen that he was, he followed you closely in the fog and kept at your heels until you reached this very house. There he intervened, and then it was, Colonel Walter, that to treason you added the more terrible crime of murder.”

“I did not! I did not! Before God I swear that I did not!” cried our wretched prisoner.

“Tell us, then, how Cadogan West met his end before you laid him upon the roof of a railway carriage.”

“I will. I swear to you that I will. I did the rest. I confess it. It was just as you say. A Stock Exchange debt had to be paid. I needed the money badly. Oberstein offered me five thousand. It was to save myself from ruin. But as to murder, I am as innocent as you.”

“What happened, then?”

“He had his suspicions before, and he followed me as you describe. I never knew it until I was at the very door. It was thick fog, and one could not see three yards. I had given two taps and Oberstein had come to the door. The young man rushed up and demanded to know what we were about to do with the papers. Oberstein had a short life-preserver. He always carried it with him. As West forced his way after us into the house Oberstein struck him on the head. The blow was a fatal one. He was dead within five minutes. There he lay in the hall, and we were at our wit’s end what to do. Then Oberstein had this idea about the trains which halted under his back window. But first he examined the papers which I had brought. He said that three of them were essential, and that he must keep them. ‘You cannot keep them,’ said I. ‘There will be a dreadful row at Woolwich if they are not returned.’ ‘I must keep them,’ said he, ‘for they are so technical that it is impossible in the time to make copies.’ ‘Then they must all go back together to-night,’ said I. He thought for a little, and then he cried out that he had it. ‘Three I will keep,’ said he. ‘The others we will stuff into the pocket of this young man. When he is found the whole business will assuredly be put to his account. I could see no other way out of it, so we did as he suggested. We waited half an hour at the window before a train stopped. It was so thick that nothing could be seen, and we had no difficulty in lowering West’s body on to the train. That was the end of the matter so far as I was concerned.”

“And your brother?”

“He said nothing, but he had caught me once with his keys, and I think that he suspected. I read in his eyes that he suspected. As you know, he never held up his head again.”

There was silence in the room. It was broken by Mycroft Holmes.

“Can you not make reparation? It would ease your conscience, and possibly your punishment.”

“What reparation can I make?”

“Where is Oberstein with the papers?”

“I do not know.”

“Did he give you no address?”

“He said that letters to the Hôtel du Louvre, Paris, would eventually reach him.”

“Then reparation is still within your power,” said Sherlock Holmes.