The Henley Regatta affords the family a short respite from London and an opportunity for Miles and Lissa to entertain family members of a visiting Belgian dignitary whom the Queen has foisted on them so they can experience English family life.

But the visitors have a secret. Both are mathematical savants, and someone is after them. After a failed assassination attempt, it becomes evident that there is more afoot, which involves an arranged marriage, a hidden document and military intelligence in the form of the handsome Duke of Ranford, the younger brother of Miles’ stepmother.

While at the Regatta, a plot to kidnap one of their guests results in Miles’ sister being nabbed by mistake, and when Lissa tries to intervene, things go from bad to worse. Resulting in a frantic chase to France in an attempt to save them.

Will the face of Brocklehurst’s leadership finally be revealed?