Sherlock Holmes and Doctor Watson 1980 S01E12

Episode: The Case of the Purloined Letter. Doctor Sergius, an unscrupulous foreign diplomat, has a compromising letter stolen from the safe of Lord Brompton in order to blackmail Brompton into recommending approval of a proposed treaty. Holmes suspects a notorious safe-cracker of having done the job, and decides to put psychological pressure on him in hopes of getting a confession naming Sergius as his employer. Inspired by Poe's The Purloined letter.