There was nothing much happening in Jerome and Benno Leuer’s yard in Hamel, Minn. on August 11, 1948. It was noontime in the thick of summer and the boys, 10 and 8, were idly playing when, as they later described it, something overhead caught their eyes. They looked up and their jaws dropped. Roughly 12 ft. up in the air was a dull gray, circular object, about 1 ft. thick and 2 ft. in diameter, slowly descending between them. They stood transfixed as the object settled onto the ground, making a clattering sound like metal hitting metal. The object rested...