What happened? What didn't? Mad Men's most plot-heavy season by far begins with plucky Peggy Olson meeting her new boss, semi-professional philanderer/brilliant ad exec Don Draper and follows the pair (and their colleagues) through a tumultuous nine-month period of secret trysts, new marriages, heart attacks, business triumphs, and the gradual revelation of Don's big secret: He's really Dick Whitman, a poor prostitute's son who stole his commanding officer's identity during the Korean War. Oh, and at the end of the season, Peggy transitions from secretary to junior copywriter…and gives birth to a surprise baby. Phew!
Essential episode: ''Nixon vs. Kennedy'' This one is a tough call: Mad Men's pilot is remarkably assured, and the first season finale contains one of the series' most iconic milestone scenes (Don's ''Carousel'' pitch). But it's ''Nixon vs. Kennedy,'' the season's penultimate episode, that best represents what makes Mad Men great and serves as the season's true climax. A raucous Election Night party pushes Sterling Cooper's office dynamics to the forefront; meanwhile, both Pete Campbell and the audience finally learn the truth about Don Draper's origins. It seems as though our antihero's career (and, perhaps, the show) might be over, until wise old Bert Cooper delivers one of TV's greatest subversions: ''Mr. Campbell, who cares?'' That alone is enough to make this hour a must-see. Hillary Busis