A Handful of Dust — Tessa Barclay

Latest title in the crime series featuring ex-Crown Prince Gregory of Hirtenstein
Gregory Crowne is hoping for a romantic interlude in France with his girlfriend Liz Blair, but their plans are shelved when they are drawn into the search for a missing investigative reporter, Barbara Rallenham, by the woman's sister. As they start to ask questions, it becomes clear that Barbara had uncovered evidence of a sinister plot with implications for national security.