We were ushered into a dim-lit drawing-room, where an instant later we were joined by a very tall, handsome, light-bearded man of fifty, the younger brother of the dead scientist. His wild eyes, stained cheeks, and unkempt hair all spoke of the sudden blow which had fallen upon the household. He was hardly articulate as he spoke of it.

“It was this horrible scandal,” said he. “My brother, Sir James, was a man of very sensitive honour, and he could not survive such an affair. It broke his heart. He was always so proud of the efficiency of his department, and this was a crushing blow.”

“We had hoped that he might have given us some indications which would have helped us to clear the matter up.”

“I assure you that it was all a mystery to him as it is to you and to all of us. He had already put all his knowledge at the disposal of the police. Naturally he had no doubt that Cadogan West was guilty. But all the rest was inconceivable.”

“You cannot throw any new light upon the affair?”

“I know nothing myself save what I have read or heard. I have no desire to be discourteous, but you can understand, Mr. Holmes, that we are much disturbed at present, and I must ask you to hasten this interview to an end.”

“This is indeed an unexpected development,” said my friend when we had regained the cab. “I wonder if the death was natural, or whether the poor old fellow killed himself! If the latter, may it be taken as some sign of self-reproach for duty neglected? We must leave that question to the future. Now we shall turn to the Cadogan Wests.”

A small but well-kept house in the outskirts of the town sheltered the bereaved mother. The old lady was too dazed with grief to be of any use to us, but at her side was a white-faced young lady, who introduced herself as Miss Violet Westbury, the fiancee of the dead man, and the last to see him upon that fatal night.

“I cannot explain it, Mr. Holmes,” she said. “I have not shut an eye since the tragedy, thinking, thinking, thinking, night and day, what the true meaning of it can be. Arthur was the most single-minded, chivalrous, patriotic man upon earth. He would have cut his right hand off before he would sell a State secret confided to his keeping. It is absurd, impossible, preposterous to anyone who knew him.”

“But the facts, Miss Westbury?”

“Yes, yes; I admit I cannot explain them.”

“Was he in any want of money?”

“No; his needs were very simple and his salary ample. He had saved a few hundreds, and we were to marry at the New Year.”

“No signs of any mental excitement? Come, Miss Westbury, be absolutely frank with us.”

The quick eye of my companion had noted some change in her manner. She coloured and hesitated.

“Yes,” she said at last, “I had a feeling that there was something on his mind.”

“For long?”

“Only for the last week or so. He was thoughtful and worried. Once I pressed him about it. He admitted that there was something, and that it was concerned with his official life. ‘It is too serious for me to speak about, even to you,’ said he. I could get nothing more.”

Holmes looked grave.

“Go on, Miss Westbury. Even if it seems to tell against him, go on. We cannot say what it may lead to.”

“Indeed, I have nothing more to tell. Once or twice it seemed to me that he was on the point of telling me something. He spoke one evening of the importance of the secret, and I have some recollection that he said that no doubt foreign spies would pay a great deal to have it.”

My friend’s face grew graver still.

“Anything else?”

“He said that we were slack about such matters - that it would be easy for a traitor to get the plans.”

“Was it only recently that he made such remarks?”

“Yes, quite recently.”