The Mazarin Stone, a famous jewel, acts as a magnet for crime. Holmes investigates the latest and perhaps most curious episode in its adventures.
The body of one Cadogan West is found in an underground tunnel near Aldgate Station, with his skull smashed, and Holmes is puzzled by the interest his brother Mycroft is showing in the case. Mycroft explains that the top secret plans for a new submarine were in the dead man's pocket, but three of the ten pages were missing when the body was found. Mycroft, on behalf of the British Government, asks his brother to find the missing pages.
John Drake travels to a Balkan country to investigate the misappropriation of funds by a Minister. Drake uncovers the plot. Involving love, politics and revenge.