Book #2 in his own series and #6 in the series.
The date is August, 1939. A group of Italians working in Corsica are suspected of espionage so Papa Pontivy, using Captain Newman for help, is called in to investigate. He soon learns that the men are in the pay of Germany, not Italy. He also discovers, over time, that their paymaster actually wants them to be caught to sour relations between France and Italy.