Speaking of whom, he's engaged in foreplay with his wife. She goes to take certain precautions, if you will, but he stops her. He pointedly tells her that he can't provide for a child on what he makes, but she firmly orders him not to worry about that. Having been subtextually reassured that the necessary money will find its way to them, he tells her to stay there. In case it isn't clear, as far as she can tell, he's checking with her to be sure that trying for a child is what she wants and that it's financially feasible, as evidenced by her joyful, "Oh, Peter!" Of course, what she doesn't know is that this is part of his plot to get her father's business, which would elicit an "Oh, Peter" in an entirely different tone of voice.
Betty's sitting at the kitchen table smoking and drinking when Don arrives home. He greets her as "Birdy," and she asks why he didn't stay in the city, given that it's 9:30 already. The irony, of course, is that now that she suspects him of cheating on her, all his side action has completely dried up. He doesn't quite tell her that, though, saying he has work to do at home and asking where the slide projector is. Not without bitterness, she notes that he's not going to spend any time with his family on the eve of not seeing them at all for four days, but she then apologizes and said she had a terrible day. She asks him to sit with her, and he complies and inquires what happened, so she relates the news about Francine, and Don's surprised that Francine even told Betty. Don of course is simply thinking Francine wouldn't want to tell anyone, but Betty takes it personally and says that Francine is like a sister to her. Don takes her hand as she bitterly says that Francine should poison Carlton, and asks how someone could do that to the person he or she loves and has children with. She pointedly asks, "Doesn't this all mean anything?" Don rhetorically asks who knows why people do what they do, but this isn't the answer Betty was looking for, as she regards him with a face dark and bitter with suspicion. He flinches first, getting up and telling her to bring the wine. Don, she said that she had a bad day, not that she had a sudden onset of amnesia.
At the office, Duck is showing Don the new slide projector (called the "Doughnut" or the "Wheel"), saying that it's "continuous and doesn't jam." Given some of the slide presentations I was subjected to in my youth, those aren't necessarily selling points, but I've seen enough of this show to know that Don will have no trouble spinning that straw into gold. Duck as much as asks him to do that, not that I blame him.