During the next week at Insel Ruegen, I watched the boat traffic from the brick mason school. The school was on a high point on the island near the boat traffic. As I laid brick during the day, I kept my eye on the comings and goings of the boat traffic. When I saw a patrol boat leave, I wrote it on a piece of paper and stuck the paper in a breast pocket of my work frock. When I saw the same patrol boat return, I marked the return on the same piece of paper.

After work classes, in the evening, I we...