Holmes is summoned by his elder brother Mycroft to the Diogenes Club in Pall Mall where he is greeted by his brother and three other recognizable government diplomacy officials. The men require Holmes's expertise immediately, stating that they are working for an unnamed noble client of the highest station, who has serious concerns on behalf of his mother, a woman they insist on calling 'Lady X' for reasons of confidentiality. A classified letter belonging to 'Lady X' has fallen into the wrong hands; this information has the potential to besmirch not only England, but the Empire as a whole. Holmes and Watson must embark on a journey to prevent this from happening, but with the added pressure of time the risk of failure is very great indeed.