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.

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.

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.

With his personal and professional life crumbling around him, Don positions himself for a change of scenery. Meanwhile, Pete's life is falling apart as well, thanks to the meddling of Bob Benson.