June 1887. As the climax of her Golden Jubilee celebrations, Queen Victoria will join more than fifty foreign monarchs and heads of state, her peers of the realm and her ministers in a service of thanksgiving at Westminster Abbey. Spymasters in the newly created Special (Irish) Branch of Scotland Yard inform the Prime Minister that blood-oath Irish Republican fanatics vow to wipe out the Queen and her family; Fenian assassins will throw bombs of terrible potency using the new explosive, dynamite. Sherlock Holmes and his companions Doctor Watson and young Winston Churchill are called in not only to prevent a dynamite outrage against the Queen, but to avert a catastrophic war that might bring down the Empire. As the plot unravels, they find it harder and harder to determine who they can trust even at the highest levels of the government. Who is spying on whom?