This episode gave Rob Lowe the chance to do show his acting chops. It starts "in medias res" with a plot line about Sam's father that serves only to put some extra dramatic dimension into what follows: Sam discovers that a man he felt was innocent - and someone's father - did in fact spy for the Soviets. The many different emotions he goes through could serve any actor as a concise summary of his craft. Rob Lowe pulls it off beautifully, never going over the top.
Of the other story lines the most interesting one is Toby's confrontation with modern day protesters and his scorn for the way they handle things. Richard Schiff is brilliant in his sarcasm, as usual, but can also suggest melancholy with a fleeting look or gesture.