Daggers and Men's Smiles

On the English Channel Island of Guernsey, Detective Inspector Ed Moretti and his new partner, Liz Falla, investigate vicious attacks on Epicure Films. The international production company is shooting a movie based on British bad-boy author Gilbert Ensor's bestselling novel about an Italian aristocratic family at the end of the Second World War, using fortifications from the German occupation of Guernsey as locations, and the manor house belonging to the expatriate Vannonis.
When vandalism escalates into murder, Moretti must resist the attractions of Ensor's glamorous American wife, Sydney, consolidate his working relationship with Falla, and establish whether the murders on Guernsey go beyond the island.
Why is the Marchesa Vannoni in Guernsey? What is the significance of the design that appears on the daggers used as murder weapons, as well as on the Vannoni family crest? And what role does the marchesas statuesque niece, Giulia, who runs the family business and is probably bisexual, really play?