S idney Rittenberg's face fills the screen in a college auditorium where The Revolutionary is being shown. His eyebrows are bold brushstrokes of white above narrowed, intent eyes. His lips are firm. He has the wrinkles and gnarled neck of an old man. He does not, however, look like a man who is 90 years old, or like one battered by spending 16 of those years in solitary confinement in China for the offense, ultimately, of believing too deeply in the Party and the revolution. "If you put one drop into the long river of human history, that's immortal ... You either make a difference or you don't make a difference," Rittenberg says to the camera in his Southern gentleman's drawl. This is his credo. Outside the auditorium windows, night has fallen. Rittenberg's larger-than-life face is reflected, translucent, in the glass, as if his memory were speaking out of the darkness. "History," he says wryly, "rolled right over me." The Revolutionary , recently released, is Sidney Rittenberg's...