Grand Duke Georgii Alexandrovich arrives in Moscow for the coronation, with three of his children. During an afternoon stroll, daughter Xenia is dragged away by bandits, only to be rescued by an elegant gentleman and his oriental sidekick. The passing heroes introduce themselves as Fandorin and Masa, but panic ensues when they realise that four-year old Mikhail has been snatched in the confusion.

A ransom letter arrives from an international criminal demanding the handover of the Count Orlov, an enormous diamond on the royal sceptre which is due to play a part in the coronation. Can the gentleman detective find Mikhail in time?