Joan and Greg's party.  Joan is racking up more compliments, and it turns out Greg's not quite the doctor wonder he's made himself out to be.  Once again Joan is a credit to him after he convinces her to play her snazzy red accordian and sing in French to impress their guests, who are suitably wowed.

Betty is filling her plate, when a very drunk Jane Sterling trips all over herself.  She manages to notice Betty's pregnant, and says she knew she and Don would get back together!  Betty looks mad enough to spit nails, and Don wisely says he'll take care of her and Betty stomps off.  Jane wonders why Don doesn't like her.  Roger wanders over and wonders what's going on.   He orders up a glass of milk for his young, drunk wife,  and confronts Don about Don giving him the cold shoulder.  He blames it on his conspicuous happiness, but Don corrects him - no one thinks Roger's happy, they think he's a fool.  Roger is ticked, and says the great thing about country clubs is you can invite who comes and keep the riff raff out.

The Draper home.  Sally tiptoes hesitantly in to say goodnight to Grandpa Gene, who gruffly orders her in his room.  Turns out it's just to continue their reading, and Grandpa Gene is an old softie who knows Sally learned her lesson and doesn't need additional punishment.  Aww!

Don watches Roger and Jane slow dance before heading off to find Betty.  She's far from the party but glows in the moonlight in her lace dress.  Silently, he walks over to her and they passionately embrace as a piano plays us into the credits.