Sherlock Holmes gets in trouble with his landlady Mrs. Hudson for not paying his rent. Holmes’ friend, Dr. Stamford, suggests Holmes get a flatmate and sends Dr. John Watson, whom Holmes deduces is a retired army doctor. Mrs. Hudson is impressed enough to allow Watson to become Holmes’ flatmate. Inspector Lestrade of Scotland Yard arrives and arrests Holmes for suspicion of murdering Count Drebber.

Sherlock is frustrated because he thinks there’s a mastermind behind the Noahtic and Drebber cases whose identity eludes him. Returning on a train after an unsatisfying investigation into another aristocrat’s death, he happens to meet William again.