"The Adventure of the Naval Treaty" is one of the 56 Sherlock Holmes short stories written by Sir Arthur Conan Doyle. It is one of 12 stories in the cycle collected as The Memoirs of Sherlock Holmes. Doyle ranked "The Adventure of the Naval Treaty" nineteenth in a list of his nineteen favourite Sherlock Holmes stories.
Dr Watson receives a letter, which he then refers to Holmes, from an old schoolmate named Percy Phelps who is now an employee of the Foreign Office. Phelps reveals that an important and secret naval treaty has been stolen from his office. It disappeared while he had stepped out of the room momentarily, late in the evening, to see about some coffee that he had ordered. His office has two entrances, each joined by a stairway to a single landing. The commissionaire kept watch at the main entrance. There was no-one watching at the side entrance. Phelps also knew that his fiancée's brother was in town and that he might drop by. Phelps was alone in the office.
Phelps pulled the bell cord in his office to summon the commissionaire, and to his surprise the commissionaire's wife came up instead. He worked at copying the treaty that he had been given while he waited. At last, he went to see the commissionaire when it had taken some time for the coffee to arrive. He found him asleep with the kettle boiling furiously. He did not need to wake him up, however, as just then, the bell linked to his office rang. Realizing that someone was in his office with the treaty spread out on his desk, Phelps rushed back up and found that the document had vanished, and so had the thief.
It seemed obvious that the thief had come in through the side entrance; otherwise he would have passed Phelps on the stairs at some point, and there were no hiding places in his office. No footprints were seen in the office despite its being a rainy evening. The only suspect at that point was the commissionaire's wife, who had quickly hurried out of the building at about that same time.
This was followed up, but no treaty was found with her. Other suspects were the commissionaire himself and Phelps's colleague Charles Gorot. Neither seemed a very likely suspect, but the police followed them both, and the commissionaire's wife. As expected, nothing came of it.
Phelps was driven to despair by the incident, and when he got back to his home in Woking, he was immediately put to bed in his fiancée's brother's room. There he remained, sick with “brain fever” for more than two months, his reputation and honour apparently gone, and his career in dire jeopardy.
Holmes is quite interested in this case, and makes a number of observations that others seem to have missed. The absence of footprints, for instance, might indicate that the thief came by cab. There is also the remarkable fact that the dire consequences that ought to result from such a treaty being divulged to a foreign government have not happened in all the time that Phelps has been ill. Why was the bell rung?
Holmes gathers some useful information at Briarbrae, the Phelps house, where his fiancée, Annie Harrison, and her brother Joseph have also been staying. She has been nursing him days while a nurse has been employed to keep watch over him at night. Joseph, it seems, is along for the ride.
After seeing Phelps at Woking, Holmes makes some inquiries in town. He visits Lord Holdhurst, Phelps's uncle, who gave his nephew his important job with the treaty, but Holmes dismisses him as a suspect, and is quite sure now that no-one could have overheard their discussion about the job. Lord Holdhurst reveals to Holmes the potentially disastrous consequences that might occur if the treaty should fall into the hands of the French or Russian embassies. Fortunately, nothing has yet happened, despite the many weeks since the theft. Apparently, the thief has not yet sold the treaty, and Lord Holdhurst informs Holmes that the villain's time is running out, as the treaty will soon cease to be a secret. Why, then, has the thief not sold the treaty?
Holmes returns to Woking, not having given up, but having to report that no treaty has turned up yet. Meanwhile, something interesting has happened at Briarbrae: someone tried to break in during the night, into Phelps's sick room, no less. Phelps surprised him at the window but could not see his face through the hooded cloak that he was wearing. He did, however, see the interloper's knife as he dashed away. This happened the very first night that Phelps felt he could do without the nurse.
Unknown to anyone else at this point - although Watson infers it from his friend's taciturnity - Holmes knows what is going on. He orders Annie to stay in her fiancé's sick room all day, and then to leave it and lock it from the outside when she finally goes to bed. This she does.
Holmes finds a hiding place near Briarbrae to keep watch after having sent Watson and Phelps to London on the train, and also letting the occupants at Briarbrae believe that he intended to go with them, ostensibly to keep Phelps out of harm's way should the interloper come back.
Holmes waits until about two o'clock in the morning, and the interloper appears out of the house's tradesman's entrance. He goes to the window, gets it open as before, opens a hidden hatch in the floor, and pulls out the treaty. He then steps straight back out the window into Holmes's hands.
The treaty has been in Phelps's sick room all the time, while the thief, Joseph, who usually slept in that room, could not get to it. He rang the bell in Phelps's office after dropping by to visit and finding him not there, but then he saw the treaty and its potential value. His inability to reach the treaty explains why there have been no dire political consequences. Holmes explains that Joseph had lost a great deal of money on the stock market, which explains his need for money. Being a very desperate and selfish man, he cared nothing for the consequences Phelps might suffer from the document's loss.
Always one with a flair for the dramatic, Holmes literally has the treaty served up to Phelps as breakfast the next morning at 221B Baker Street, where he has spent the night under Watson's watchful eyes (although there has been no danger). Phelps is ecstatic, Holmes is quietly triumphant, and once again, Watson is dumbfounded.
Holmes explains that several clues all pointed to Joseph: the fact that the thief knew the ways of the office well, given that he had rung the bell before seeing the treaty, and that Phelps mentioned his relatives had been shown around; the fact that Joseph had intended to stop in and see Phelps on his way home, and that the theft had been committed very soon before the train would depart for Woking; that the thief had come in a cab, given that it was a rainy night but that there were no wet footprints in the passage; and the fact that the burglar who tried to break into Phelps's room was familiar with the layout of the house.
- The story gives the modern reader two incidental interesting insights into the period of its writing. First, that at the time it was in no way shameful for a government official to admit that he got his job directly by the favour of his uncle, a cabinet minister – nepotism in the most literal sense. Secondly, that when the story was written, France and Tsarist Russia – who were to become Britain's staunch allies in the First World War – were perceived as enemies. In a spy story set in his present, it was as natural for Doyle to portray these two countries as the potential purveyors of the stolen naval treaty as it would have been to portray the Soviet Union in that role in a Cold War spy thriller. And in fact, this story is one of the very first in the emerging genre of spy story.
- This is the longest of the short stories published in The Strand Magazine before Sherlock Holmes's 'death' in "The Final Problem". As such, it was originally published in two parts: the first describes the events before the interview with Lord Holdhurst, while the second explains all events thereafter.
- This story contains the first reference to "The Adventure of the Second Stain", which would not be published until around 11 years later.
- The school buildings "rising up above the slates, like brick islands in a lead-coloured sea", which Holmes points out to Watson from a train near Clapham Junction still exist today, and can still be seen by passengers on that railway line.
- "The Naval Treaty", an episode of the 1960s BBC television adaptations, from the programme's second series. Shot in colour, first aired in October 1968. Starring Peter Cushing and Nigel Stock. Unfortunately, this is one of the second series' missing episodes.
- "The Naval Treaty", the 1984 episode of the ITV / Granada Television series, starring Jeremy Brett and David Burke.
- BBC Radio 4 adapted the short story under the same name in 1992, as part of a long-term series of BBC radio adaptations of the whole Sherlock Holmes Canon, directed by playwright and radio drama director Bert Coules. The radio adaptation starred Clive Merrison and Michael Williams.
- "The Great Game", the third episode of the first series of the BBC series Sherlock, uses several of Doyle's stories as inspiration, most notably "The Adventure of the Naval Treaty" and "The Adventure of the Bruce-Partington Plans", which likewise deals with the theft of government papers related to the navy.
- "Art in the Blood", the twenty-third episode of the second season of Elementary, is inspired by the story.