As Vigata celebrates St George’s Day, an elderly man, born locally, returns to Sicily after having lived in America for many years. On the same day a diary dating from WWII is discovered hidden in an old bunker. Inspector Montalbano is entrusted with the dark secrets revealed in the diary and starts to research the time around which it was written. But during his investigation, a 90-year-old businessman is found murdered in his own home. Montalbano starts to think that the events cannot possibly be unrelated.