Don continues to conceal his increasingly complicated personal life, even in the face of Roger Sterling's invitation to open up. Meanwhile, Peggy pines for the absent Pete still on his honeymoon while fending off the advances of several of the men of Sterling Cooper.

Pete returns from his honeymoon, excited about his new marriage, but conflicted about his past encounter with Peggy. After his business relationship with Rachel takes an unforeseen turn, Don attends a party which further illuminates his increasing dissatisfaction with his present life.

Pete's professional and personal lives become more complicated as he struggles to assert power in both. While facing pressure from his wife regarding a new apartment, he further alienates Don and endangers his own position at Sterling Cooper.

A taboo office romance is revealed. At a brainstorming session, Peggy proves to be more than a secretary, opening up new opportunities for her at Sterling Cooper. Meanwhile, Rachel faces her conflicted feelings for Don after he seeks out her advice on a new campaign.

Roger joins Don for an evening of dinner and drinking, during which Roger's behavior leads to a rift in their friendship. Though Don accepts his apology, there are further consequences for Roger. Pete faces trouble at home as he continues to struggle with the demands of his new marriage.

Don is tormented as pieces of his secretive past begin to haunt him. Peggy's new success at work, and resulting boost in confidence, threaten her office relationship. Salvatore Romano gets a little too close with a client.

A rival ad agency courts Don, involving Betty in their attempt to lure him from Sterling Cooper. As the presidential campaign heats up, the agency looks for new ways to counter the latest Kennedy ads. Tempers flare over Peggy.

Don loses an account. Roger, stuck in the city for Labor Day weekend, attempts to cheer him up. Meanwhile, Joan has a night out on the town with her roommate.

Peggy is given a difficult assignment. Roger's work problems provide new opportunities for Don, and Pete grows more frustrated. Betty finds a new outlet for her growing dissatisfaction.

On election night, the Sterling Cooper staff pulls a rowdy all-nighter while watching the returns. Pete's ambitions cause him to directly challenge Don. Don remembers his past as a soldier in the Korean War.

As Thanksgiving approaches, Don's work responsibilities interfere with his domestic life. Peggy is given a new opportunity, provoking the ire of some of her colleagues. Betty makes a startling discovery.