Pressure from his boss and a skin-cream client produces a talking boil on a British adman's neck.
Mary Morstan has received a pearl in the post every year since her father's disappearance. This leads Holmes and Watson to the truth about a secret pact between four convicts during the Indian Rebellion of 1857.
Tsar Nicholas II, the inept last monarch of Russia, insensitive to the needs of his people, is overthrown and exiled to Siberia with his family.
