The Emperor's Candlesticks by Emma Orczy

THE EMPEROR'S CANDLESTICKS is a compelling tale of espionage and intrigue set in the final years of the Russian Empire. On learning that a Cardinal d'Orsay has agreed to convey some hollow candlesticks from the Emperor to a princess in St. Petersburg, two spies both see the possibility of using them to convey messages safely into Russia. When the candlesticks go missing, the two engage in a race to get them back, both realizing that their very lives could depend on the retrieval.