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 and John, searching for the true criminal who killed Count Drebber, set a trap for the criminal using the wedding ring they found at the murder scene. Sherlock is able to deduce who the real killer is, who offers Sherlock a strange deal.