The monotony of thick
smog-shrouded London is broken by a sudden visit from Holmes' brother
Mycroft. He has come about some missing, secret submarine plans. Seven of the ten plans have been found with Arthur Cadogan West's body, but the three "most essential" papers are still missing. West was a young clerk in a government office at
Royal Arsenal,
Woolwich, whose body was found next to the
Underground tracks near the
Aldgate tube station, his head crushed. He had little money with him (although there appears to have been no robbery), theatre tickets, and curiously, no Underground ticket. from 1908 showing the District and Metropolitan lines with Aldgate at right and Kensington at lower left
Inspector Lestrade tells Holmes that a passenger reported hearing a thud, as though a body had fallen on the track, close to where West's body was found. The passenger could not see anything, however, owing to the thick fog. After an examination of the track near Aldgate, Holmes concludes that West had been killed elsewhere, was deposited on the roof of an Underground train, and fell off when the jarring action of going across a
railway point at Aldgate shook the coach. Holmes decides to visit Sir James Walter, who was in charge of the papers. He has, however, died, apparently of a broken heart from the loss of his honour when the papers were stolen, according to his brother Colonel Valentine Walter. On visiting West's fiancée, Holmes learns that West had something on his mind for the last week or so of his life; he had commented on how easily a traitor could get hold of "the secret" and how much foreign agents would pay for it. On the night in question, West and his fiancée were on their way to the theatre, when he suddenly dashed off into the fog and did not return. Holmes next goes to the office from which the plans were stolen. Sidney Johnson, the senior clerk, tells Holmes that, as always, he was the last man out of the office that night, and that he had put the papers in the safe. Anyone coming in afterwards to steal them would have needed three keys (for the building, the office, and the safe), but no duplicates were found on West's body, and only the late Sir James had all three keys. Johnson also mentions that one of the seven recovered papers includes a unique invention, without which the submarine could not be properly built. Holmes also discovers that it is possible to see what is happening inside the office from outside, as the iron shutters do not close properly. in ''
Collier's'' After leaving, Holmes finds that the clerk at the nearby Underground station remembers seeing West on the evening in question. Deeply shaken by something, he had taken a train to
London Bridge. Acting on information from Mycroft, and on what he has learnt thus far, Holmes identifies a person of interest: Hugo Oberstein, a known foreign agent who left town shortly after West's murder. Some small reconnaissance shows Holmes that Oberstein's house backs onto an above-ground portion of the Underground line; furthermore, owing to traffic at a nearby junction, trains often stop right under his windows. It seems clear that West's body was laid on the train roof just there. Holmes and Dr. Watson break into Oberstein's empty house and closely examine the windows, finding that the grime has been smudged, and there is a bloodstain. An underground train stops right under the window. Some messages from the
Daily Telegraph agony column, all seeming to allude to a business deal, are also found, posted by "Pierrot". Holmes posts a similarly cryptic message in the
Daily Telegraph demanding a meeting, signing it Pierrot, in the hopes that the thief might show up at Oberstein's house. It works. Colonel Valentine Walter shows up and is stunned to find Holmes, Watson, Lestrade, and Mycroft all waiting for him. He confesses to the theft of the plans, but swears that it was Oberstein who killed West. West had followed the Colonel to Oberstein's and then intervened, and Oberstein had dealt West a fatal blow to the head. Oberstein then decided, over the Colonel's objections, that he had to keep three of the papers, because they could not be copied in a short time. He then got the idea of putting the other seven in West's pocket and putting him on a train roof outside his window, reasoning that he would be blamed for the theft when his body was found. Deep in debt, Colonel Walter had acted out of a need for money. He redeems himself somewhat by agreeing to write to Oberstein, whose address on the Continent he knows, inviting him to come back to England for the fourth, vital page. This ruse also works; Oberstein is imprisoned, and the missing pages of the plans are recovered from his trunk. Colonel Walter dies in prison, not long after starting his sentence. For his efforts, Holmes is given an emerald tie pin by "a certain gracious lady", implied to be
Queen Victoria, as the pin was received at
Windsor in the 1890s. ==Publication history==