Don will ask Megan for a divorce.
Ted will realize that he's betraying his wife, lusting for Peggy. He'll ask his wife for a trial separation, get drunk, call Peggy. She'll rush to his bachelor pad and they'll end up in bed.
Ginsburg gets run over by a car while strolling with Ken Cosgrove, who becomes paralyzed with guilt - thinking it should have and could have been him. (No, the car is not a Chevy.)
Henry Francis announces a Senate run. Betty is given a dressing down by Mother Francis about how to be a good political wife.
Pete Campbell ends up alone at the office, late, with Benson - in a compromising position. Don walks in on them -- stiffens at first but pretends to shrug it off. Now Pete and Don each know a secret about the other.
Sterling suffers another heart attack after a fight with Joan over his son while at an outdoor pool party. He falls into the pool. He's rushed to the hospital. We do not know if he makes it. We see Joan by his side, trying to remain composed.
You heard it here first.