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.

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.

With 48 minutes remaining before the train reaches the next station, Sherlock declares that William and he can find the murderer in time. Sherlock relies on the evidence at the scene, while William pursues a psychological profile of the killer.

Receiving a new name, Bonde joins the Moriarty ranks, and is sent to retrieve the contents of a safe deposit box with Moran, Louis, and Fred. But when an unexpected bank heist spurs the others into spontaneous action, Bonde is left wondering what to do.

A series of murders is being carried out by someone claiming to be Jack the Ripper. In response, a vigilante group of the town's poor confronts Scotland Yard while William and the real Jack scramble to uncover the true culprit's aims and foil their plans.

A culprit is arrested in the Jack the Ripper case which was solved by the Moriartys. Suspecting a frame-up by Arterton, Lestrade asks Sherlock for help in finding evidence that would prove it. Meanwhile, Paterson works to sneak Bonde inside the station.

John introduces Sherlock to Mary, his fiancée. A stunned Sherlock realizes that Mary has another concern. She produces six pearls, detailing their connection to her missing father. She asks Sherlock to look into the matter, but is holding something back.

When William James Moriarty claims responsibility for being the Lord of Crime in all the papers, aristocratic condemnation and public anger falls upon the Moriartys. The final problem of the Moriarty Plan that William has concocted at long last begins.