I was a bicycle mechanic in Lille when the Germans came. In 1942, the Resistance recruited me because I could repair anything — including a German Enigma component that had been salvaged from a crashed plane. My job was to courier messages between the Pas-de-Calais network and the British intelligence station in London. I bicycled 80 kilometers a week carrying microfilm messages sewn into the linings of my coat. The Gestapo had a photograph of me — taken by a collaborator — that circulated through every police station in northern France. I disguised myself: grew a mustache, changed my posture,...