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.

A reporter named Mullen 'stumbles' onto a story linking a prominent Member of Parliament to a KGB agent and a near-nuclear disaster involving a teenage runaway and a U.S. Air Force base. Has there been a Government cover-up? Mullen teams up with Vernon Bayliss, an old hack, and Nina Beckam, the MP's assistant, to find out the truth.

Sherlock Holmes uses his abilities to take on cases by private clients and those that the Scotland Yard are unable to solve, along with his friend Dr. Watson.