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.

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.

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.

In the third-season opener, Salvatore and Don take a business trip out of town. Pete Campbell and Ken Cosgrove worry about the changes at Sterling-Cooper and how the changes will impact them.

Don has a big meeting with Connie about their future relationship. Betty is the beneficiary of some interesting advice and Pete has a serious sit-down with some clients.

While Don continues his affair with Sylvia, Pete's latest infidelity threatens his marriage. Meanwhile, Peggy's icy relationship with her new staff continues, but she also gets an unlikely tip on a potential new client.

The creative department has a wild, drug-influenced weekend as they work on the Chevy account, Don has trouble letting go of Sylvia, and Sally walks in on an unwelcome intruder.