“Apparently not. There is a list here of his possessions. His purse contained two pounds fifteen. He had also a check-book on the Woolwich branch of the Capital and Counties Bank. Through this his identity was established. There were also two dress-circle tickets for the Woolwich Theatre, dated for that very evening. Also a small packet of technical papers.”

Holmes gave an exclamation of satisfaction.

“There we have it at last, Watson! British government — Woolwich. Arsenal — technical papers — Brother Mycroft, the chain is complete. But here he comes, if I am not mistaken, to speak for himself.”

A moment later the tall and portly form of Mycroft Holmes was ushered into the room. Heavily built and massive, there was a suggestion of uncouth physical inertia in the figure, but above this unwieldy frame there was perched a head so masterful in its brow, so alert in its steel-gray, deep-set eyes, so firm in its lips, and so subtle in its play of expression, that after the first glance one forgot the gross body and remembered only the dominant mind.

At his heels came our old friend Lestrade, of Scotland Yard — thin and austere. The gravity of both their faces foretold some weighty quest. The detective shook hands without a word. Mycroft Holmes struggled out of his overcoat and subsided into an armchair.

“A most annoying business, Sherlock,” said he. “I extremely dislike altering my habits, but the powers that be would take no denial. In the present state of Siam it is most awkward that I should be away from the office. But it is a real crisis. I have never seen the Prime Minister so upset. As to the Admiralty — it is buzzing like an overturned bee-hive. Have you read up the case?”

“We have just done so. What were the technical papers?”

“Ah, there’s the point! Fortunately, it has not come out. The press would be furious if it did. The papers which this wretched youth had in his pocket were the plans of the Bruce-Partington submarine.”

Mycroft Holmes spoke with a solemnity which showed his sense of the importance of the subject. His brother and I sat expectant.

“Surely you have heard of it? I thought everyone had heard of it.”

“Only as a name.”

“Its importance can hardly be exaggerated. It has been the most jealously guarded of all government secrets. You may take it from me that naval warfare becomes impossible within the radius of a Bruce-Partington’s operation. Two years ago a very large sum was smuggled through the Estimates and was expended in acquiring a monopoly of the invention. Every effort has been made to keep the secret. The plans, which are exceedingly intricate, comprising some thirty separate patents, each essential to the working of the whole, are kept in an elaborate safe in a confidential office adjoining the arsenal, with burglarproof doors and windows. Under no conceivable circumstances were the plans to be taken from the office. If the chief constructor of the Navy desired to consult them, even he was forced to go to the Woolwich office for the purpose. And yet here we find them in the pocket of a dead junior clerk in the heart of London. From an official point of view it’s simply awful.”