Villainous Saltpetre

In 1930, Guy Brangley, an unsuccessful playwright, stages his own disappearance in order to provoke publicity.Twenty-five years later his body was recovered from the sea, three days after he was last seen by anyone. Was this the tragic result of yet another publicity stunt? Or had Brangley been pushed from the battlements of his home, Pengawnen Castle?
Villaneous Saltpetre is one of Clifford Wittings most engaging novels, set in that favourite corner of the British Isles for murder mysteries, Cornwall. However the book opens with a scene from the French Revolution in a little coastal town in Brittany where the Comte de Tournel is preparing to to leave the country with his wife and daughter and join the emigrés who were plottong to restore the former regime.
What could possibly connect these events?