Inspector Maigret (four-time César nominee Denis Podalydès, in a tremendous performance) is urgently summoned to the Quai d'Orsay: a former ambassador has been found dead by his long-serving housekeeper (Anne Alvaro, The Taste of Others). But rather than contact the police, she has followed diplomatic protocols by first informing the Ministry of Foreign Affairs. Forewarned that he will find a series of salacious letters – and cautioned to be discrete - Maigret heads to the victim’s opulent apartment. He finds no forensic evidence at the crime scene, but certainly, the letters prove startling – secret, decades-spanning correspondence between the ambassador and the Princess of Vuynes, whose own husband, by strange coincidence, has also just died…