Michael Pearce, A Dead Man in Malta
Sandor Seymour of the Special Branch is sent to investigate the deaths of three men in a naval hospital on Malta. All three (two British sailors and one German balloonists) were admitted with relatively minor injuries, and all three died of "respiratory failure." A letter from an Englishwoman travelling in Malta raised questions about the deaths, and Seymour's job required (a) that he clear up any mystery surrounding the deaths and (b) prevent any conflict between the British government of the island, the local police force, and the Navy.
His fiancé Chantale manages to join him there (volunteering as a member of a British women's nursing auxiliary--headed by the woman who wrote the letter that triggered the investigation).
My two favorite characters were Sophia, a Maltese girl, and Kevin, son of the meddling Englishwoman. They both have school papers to write and wind up helping each other, and, in the process, doing some growing up. (I could see a book in which they are the main characters.)
Seymour investigates in his usual manner--talk to everyone, alarm no one, slowly put all the pieces together. I thought the last part was a bit perfunctory, but this is a solid entry in a very good series.