Mask of Treason — Anne Stevenson

Lovely, independent Fiona Grant, a costume designer in the London opera world, returns for a holiday to her parents' home in the Scottish Highlands. On the way she meet imperturbable Max Wyndham, a naval officer on an investigative mission regarding leaks of military information from a naval base near Fiona's home. At some point everyone is a likely suspect -- Fiona, her parents, even a star of the opera. Roles are constantly changing in a diverting way, until the final chapters bring a deadly game to a satisfying halt.