Christopher Nolan’s mega-hit Oppenheimer features dozens of historical characters, but among them you won’t find Ted Hall. And yet Hall, who went to work on the Manhattan Project as a teenage wunderkind physicist, occupies a significant place in the overall story. As a fresh-faced and idealistic youth, he shared top secret details of the atom bomb’s design with Soviet agents — but he was never prosecuted for it. The incredible tale of Hall’s act of espionage, and the moral considerations that motivated him, is told in Steve James’ new documentary A Compassionate Spy. Magnolia Pictures opens the documentary in limited...