An Ann-Margret look-alike auditions for the Patio Cola ad; Peggy chides Harry for requesting a gratuitous encore. Ken and Pete notify Peggy, Smitty, and Paul that new concepts are needed for the Bacardi rum account. They'll have to work all weekend to generate them while the two account heads and Harry attend a country club party Roger and Jane are throwing.
Jane, dressed to the nines, runs into Joan at the office. "It's so great to see you," she tells Joan, then requests that Joan have "one of the girls" tend to her driver. Meanwhile, Olive, Peggy's new middle-aged, matronly secretary, tries to anticipate her needs but fails.
That night at the Draper home, Sally reads to Gene from The History of the Decline and Fall of the Roman Empire. "You just wait. All hell's gonna break loose," her grandfather warns her.
The Saturday Bacardi session goes slowly: Peggy, Paul, and Smitty sip rum for inspiration, though the guys conclude that marijuana would spark creativity better than booze.
Sally steals five dollars from Gene. She says nothing when he later notices it missing. Betty assumes her father is just being forgetful.
Joan and Greg tidy up their apartment for a Saturday night dinner party. Greg wants to seat Ronald Ettinger, the Chief of Surgery, at the head of the table. "Not in your home," instructs Joan, citing etiquette expert Emily Post. Joan mollifies her husband with a compromise: They'll serve buffet style, rendering seating order moot.
Jeffrey, Paul's upper-crust Princeton pal, arrives at Sterling Cooper to sell Paul and Smitty some joints. Olive, who has come to work to support Peggy, smells the pot and warns Peggy not to participate. Peggy ignores her. "I want to smoke some marijuana," Peggy informs Jeffrey.
At the country club, Roger, on his knees in blackface, croons "My Old Kentucky Home" to Jane. "Can we go?" Don whispers to Betty, who wants to stay. Don wanders off to an untended bar where he meets an older male wedding guest. Don prepares Old-Fashioneds while the two swap stories about their modest beginnings.
Back at Sterling Cooper, Paul, still high, orders Jeffrey out of the office for disparaging Paul's Jersey accent and lack of means during their student days. Jeffrey counters by impugning Paul's singing ability (the two sang together in the Tigertones, one of Princeton's a capella groups). Challenged to prove otherwise, Paul belts out "Hello My Baby," and they finish the ditty together with a flourish. "I am so high," says Peggy.
A well-groomed man at the party asks Betty about her pregnancy. "I'm going to blame this on martinis," he says before requesting permission to touch her belly, which she allows.
At Joan's party, Irene Ettinger, Ronald's wife, offers tips about marriage to a young doctor, chief of which is to avoid getting pregnant. "The fact that Greg can get a woman like you makes me feel good about his future no matter what happens," Irene says.
At home, Gene continues to grouse about his missing money. Sally tosses the bill onto the floor then asks, "Grandpa, is this it?" Saying it is, Gene stares at Sally.
Cooper and Roger introduce Betty and Don to Henry Francis, the man who felt Betty's belly. Henry, Cooper and Roger explain, has just attended the marriage of his boss, New York governor Nelson Rockefeller, to a divorcee -- an act of political harakiri, according to Cooper. "Why did Rocky marry her?" Jane asks of the bride. "They're in love," Henry responds. "Oh," Jane coos to Roger.
Paul, lying on the floor, ruminates on geopolitics. Smitty suggests they all head to the building's roof, prompting Peggy to visualize a Bacardi scenario. The guys can go home if they want, she says, "I'm in a very good place right now."
Olive frets about Peggy's marijuana smoking and its repercussions, but Peggy says she's "not scared of any of this." Sensing that Olive is worried for her, Peggy reassures her. "I am going to get to do everything you want from me," she says.
At Joan's, the conversation turns to the hospital and a mishap that occurred while Greg was performing surgery. To deflect attention from himself, Greg encourages Joan to play her accordion for the guests. She accedes, deftly singing "C'est Magnifique."
Back at the party, Betty and Don assist Jane, who tipsily blurts out "I knew you two would get back together. I never had any doubt, no matter what the problem was." Betty, glaring, departs while Jane grabs Don's belt and complains, "You don't like me. I'm a nice person." When Roger arrives, Don tells him Jane is drunk. "I don't know what I did to get under your skin," Roger says, adding that he made a mistake by being conspicuously happy. "No one thinks you're happy," Don replies. "They think you're foolish."
At bedtime, Sally enters Gene's room. He looks sternly at her before handing her The History of the Decline and Fall of the Roman Empire to read aloud again.
Roger and Jane slow dance as Don leaves the club. Walking across the lawn, he approaches Betty, who stands alone in the moonlight. The two embrace.