The Adventure of the Bruce-Partington Plans recap

Mycroft asks Holmes to investigate the death of government clerk Arthur Cadogan West, whose body is found beside an Underground line with most of the stolen Bruce-Partington submarine plans in his pocket. Holmes notices that West could not have reached the place in the ordinary way and concludes that his body fell from the roof of a train. A nearby house belongs to foreign agent Hugo Oberstein. There Holmes finds evidence that West was killed after following the real thief, Colonel Valentine Walter, who had taken the plans to sell them and escape his debts. Oberstein retained the crucial pages and used the railway to dispose of West's body. Holmes exploits Oberstein's coded newspaper correspondence, obtains Walter's confession and cooperation, recovers the papers, and clears West of treason.

Mycroft Holmes brings news that Arthur Cadogan West, a young clerk at Woolwich, has been found dead beside an Underground railway. Seven sheets from the highly secret Bruce-Partington submarine plans are in his pocket, but three essential sheets are missing. The evidence suggests theft and attempted sale, yet West's fiancée describes him as loyal and deeply worried about the plans' security. Holmes also finds problems with the location of the corpse: West had no ticket, and the body shows no ordinary explanation for reaching the track. He infers that it rode on the roof of a train and fell at a curve. The route points to a house beside the line occupied by known foreign agent Hugo Oberstein. Holmes and Watson enter the empty house and find signs that a man was killed there and then passed through a window onto a stationary train. A coded newspaper correspondence leads Holmes to Colonel Valentine Walter, brother of the official responsible for the plans. Walter confesses that debt drove him to steal them for Oberstein. West saw him, followed him, and confronted the spy; Oberstein killed West, planted the less vital papers on him, and kept the crucial sheets. Walter agrees to send a message designed to draw Oberstein into a trap. The missing plans are recovered, West is cleared of betrayal, and the government recognizes Holmes's service in protecting the project.

Holmes identifies Colonel Valentine Walter as the person who stole the plans to pay his debts. Cadogan West saw the theft, followed Walter to Hugo Oberstein's railway-side house, and confronted the spy. Oberstein killed West, kept the most valuable pages, and placed the body on the roof of a stopped train; it fell beside the line later in the journey. Confronted through a coded newspaper exchange, Walter confesses and agrees to help the authorities lure Oberstein back within reach of British justice. The missing papers are recovered, West's name is cleared, and the government rewards Holmes for preventing the defense secret from remaining in foreign hands.