The Adventure of the Naval Treaty (1893) is a short story in which Dr. Watson brings Sherlock Holmes a case involving his old schoolmate Percy Phelps, a rising young clerk at the Foreign Office. Phelps has lost a highly sensitive naval treaty entrusted to him for copying; it vanished from his desk during a brief absence, leaving him under a cloud of suspicion and in a state of nervous collapse. Holmes travels to the countryside to examine the scene and the people around Phelps, including his fiancée Annie Harrison and her brother Joseph. Through careful observation of small inconsistencies at both the office and the house, Holmes uncovers that the theft was an inside job driven by personal greed rather than foreign espionage. In a characteristically theatrical recovery, he restores the missing document, clears Phelps’s name, and leaves the young man with a memorable lesson on the value of even the smallest details.