In the fall of 1964, Don flubs a publicity opportunity, costing Sterling Cooper Draper Pryce an account and leaving Lucky Strike responsible for much of the agency’s revenue. Given a second chance at self-promotion, Don shines. A publicity stunt Pete and Peggy stage goes awry but increases the client’s sales. Don begins dating Jane Sterling‘s friend Bethany but also hires a hooker to abuse him, and Peggy’s boyfriend, Mark, presses her to have sex.
Sally reconnects with Glen Bishop, who predicts her family will soon move and then trashes her house, sparing only Sally’s room. Freddy Rumsen brings the agency Pond’s Cold Cream. Peggy finds his concepts dated but considers his advice about sex. Bert Cooper hires a consumer-research firm whose consultant, Dr. Faye Miller, pegs the skeptical Don with her own prediction: he’ll remarry within a year. Lucky Strike’s Lee Garner Jr. demeans Roger at the office Christmas party; Don has a drunken tryst with his secretary, Allison; and Peggy has sex with Mark.
Past abortions and Greg’s possible deployment to Vietnam complicate Joan‘s desire to become pregnant. Don cuts short his Christmas vacation after learning in Los Angeles that Anna is dying of cancer. “I know everything about you,” Anna remarks, “and I still love you.” Lane manages to insult Joan and alienate his wife at the same time. He and Don spend New Year’s Eve on the town before ending up at Don’s apartment with hookers.
Roger and Lane order Pete to drop Clearasil to placate Pond’s, but he instead pressures his father-in-law, Tom, into awarding SCDP more Vicks business. Trudy becomes pregnant, and the prospect of fatherhood delights Pete. During a Pond’s focus group that Faye moderates, Don watches uncomfortably as Allison sobs about men using women. Peggy consoles Allison, but bristles when Allison assumes Peggy also had sex with Don. Allison quits and the elderly Miss Blankenship replaces her. A lesbian named Joyce courts Peggy, who in turn charms Joyce’s writer friend Abe.
Ted Chaough of rival agency CGC brags about snagging two accounts from Don. Pete and Roger nearly come to blows after Roger insults Honda executives about World War II, setting the stage for another Chaough victory, but Don studies Japanese culture and tricks Ted into committing a costly faux pas. Sally hacks off her hair and gets caught playing with herself, prompting Betty to seek out Dr. Edna, a child psychiatrist.
Don wins a Clio Award for his Glo Coat floor wax commercial but has to hire Jane’s hapless cousin Danny Siegel after drunkenly pitching Danny’s tagline to Life cereal. Roger, compiling his autobiography, flashes back to Don hustling him for work at the old Sterling Cooper. Peggy complains to Stan about receiving insufficient recognition for her Glo Coat contributions and strips naked to make a point about his lack of creativity. Lane incenses Pete by hiring Ken Cosgrove, but the two reach a working agreement.
On her 26th birthday, Peggy declines Duck‘s offer to start a new agency together. Don abandons Roger to work late on the Samsonite concept with Peggy, which ruins Mark’s birthday surprise. Peggy and Don argue over credit for her creative contributions, but over dinner she admits her work fulfills her. Back at the office, Don, drunk, vomits. Duck appears, calls Peggy a whore, and decks Don. During the night, his head on Peggy’s lap, Don sees a ghostlike vision of Anna toting a suitcase. He learns the next morning she is dead.
Betty encounters Don at a restaurant with Bethany and becomes agitated, prompting speculation from Henry about Don’s residual place in Betty’s heart. Peggy fires freelancer Joey for disrespecting Joan, who criticizes her for proving Joan a “meaningless secretary” and Peggy a “humorless bitch.” Don invites Faye to dinner but surprises her by concluding the evening with merely a kiss. Betty describes seeing Don to Francine, who warns, “Don has nothing to lose, and you have everything.” When Don unexpectedly attends Gene’s birthday party, Betty maintains her composure.
Don and Faye begin having sex. Abe employs a ruse to see Peggy that flatters her but then scorns her work for Fillmore Auto Parts, which discriminates against blacks. He apologizes via an essay that further irritates Peggy, though she wonders later whether she’s angry or lovesick. Sally sneaks into the city to see Don and throws a tantrum when Betty retrieves her. Faye proves unable to calm Sally, though the receptionist, Megan, does. Faye says she feels like she failed a test. Roger’s flirtations annoy Joan, but after Miss Blankenship dies Joan consents to have dinner with him. Afterward, they get mugged and have sex in an alley.
Joan informs Roger she’s pregnant with his child but says she’ll handle the matter herself. Lane’s father canes him into submission after he falls for a black Playboy Bunny and refuses to return to his family. Government agents investigate Don for the North American Aviation account because Megan, now his secretary, submitted a request for security clearance with inaccuracies on it, not knowing his past. Experiencing panic attacks and fearing arrest for desertion, Don demands Pete dump the account. Pete reluctantly does, covering for Don with the partners. At the same meeting, Roger fails to reveal that Lucky Strike has dropped SCDP and pretends not to know even after someone tips off Ken.
At the hospital where Trudy is about to give birth, Tom advises Pete to abandon SCDP. Some clients defect, including Glo Coat. Don chews out Pete, saying fatherhood is distracting him, and pressures Faye for hints about unhappy clients at other agencies. She refuses on ethical grounds but eventually arranges a meeting with Heinz. In the meantime, Don and Megan have sex, and Stan takes revenge after Peggy rebuffs his advances.
The Heinz executive acknowledges Don’s creativity but worries about SCDP’s survival. Betty insists on leaving Ossining after catching Sally and Glen together. Philip Morris cancels a pitch meeting because, Don observes, SCDP’s desperation is obvious. Don places a full-page anti-tobacco ad in the New York Times to “change the conversation” about the agency. The American Cancer Society phones, but Faye’s company resigns to avoid offending other tobacco clients. Bank credit that Lane arranges requires collateral from the partners, and Don pays Pete’s share, but despite the cash infusion Danny and other staffers are let go.
Don pitches ideas to receptive cancer-society board members, and Pete and Roger scheme to pursue their corporate business. Betty fires Carla for allowing Glen in the house to say good-bye to Sally, so Don asks Megan to accompany him and babysit the kids in Los Angeles. Her ease with them endears her to him, and he proposes marriage. Their engagement upstages Ken and Peggy’s success signing Topaz Panti-Hose, SCDP’s first new business since Lucky Strike’s departure.
A tearful Faye remarks that Don only likes “the beginnings of things.” Greg, meanwhile, asks Joan when she intends to disclose she’s pregnant. Don and Betty reminisce about moving into the Ossining house, and though taken aback by his engagement Betty congratulates him. That night in his apartment, Don stares out the window as Megan sleeps.