While investigating an explosion that kills two people, Sherlock discovers a crime that’s been lying dormant for years. Meanwhile, Watson encourages Sherlock to finally pick a sponsor.

Holmes and Watson’s new careers as consultants for Scotland Yard in London take them inside the tabloid journalism industry when a popular model is the victim of an acid attack. Also, as Watson grows increasingly homesick for New York, Captain Gregson is wracked with guilt over his unresolved rift with his former consultants.