Harry gets in trouble for a snafu involving a poorly-placed television ad, and asks Roger for a subordinate to help read scripts and head off potential problems. Joan (who's almost surely pregnant, not that that's a huge surprise if you've been paying attention to her measurements) ends up taking over the job with not only her usual assured skill but also quite a bit of genuine enthusiasm. However, her success makes Harry look so good that Roger springs for a permanent subordinate, which royally pisses Joan off, although, she keeps it to herself for the moment.
Father Gill encourages Peggy to get more involved with the church, and enlists her for some PR help for an upcoming church dance. He then encourages her to talk to him about anything that might be bothering her, and he almost succeeds, but not quite.
Finally, Betty's being short with Don, which he thinks is due to nervousness about a important upcoming business dinner party they're throwing at their house for the purpose of schmoozing that guy from two episodes ago who did the Cuba campaign, but is of course because of Jimmy spilling the beans about Don and Bobbie. After the party, Betty finally straight-up confronts Don, and although Don tries to deny it and turn things around, Betty holds fast and calls him a liar as well as a cheat. Infuriated by his steadfast refusal to admit his guilt, she searches his things but doesn't find anything, so she changes tacks and asks if Don actually loves her. He tells her he does, and seems to mean it, but it isn't enough, and the next day, she calls him at work and tells him not to come home, so Don stays at the office, powerless and alone.
Through a few quick cuts, we see Betty riding her cantering horse. When she dismounts, she looks completely spent, the weight of the revelation that Don's still cheating on her causing her to lean up against the horse for support. The horse is like, "How do you think I feel? And you should hear what my stallion does with the other fillies that he thinks I don't know about." Later, after Betty enters the house, we cut to her starting to get out of her riding clothes as Don, still in bed, comes to. He looks at the clock and asks when she got up, and she replies that she doesn't know before mentioning that he said he was going to fix an outlet in the kitchen that's apparently not working. Don resists, so Betty flatly tells him that he just needs to unscrew the fuse and replace the plug. He smiles that it sounds like she could do it, but she's in no mood for levity, so he gives in. He asks her to sit down, and after she unwillingly complies, he tells her that they have a week before "this party," and it doesn't have to be a big deal, but she tartly replies that she's going to have a house full of people. "I'd appreciate it if you'd take care of the things on the list." If they're making lists now, this marriage is in even more trouble than I thought. He plays the "Birdy" card and assures her he'll fix it, and she thanks him.
Peggy shows up at Anita's, and the energy between them is much more relaxed than we've seen before, which is interesting. Anita tells her that her timing is perfect. "Ma just left." Heh. Apparently Anita's husband Gerry's back has gotten worse since we last saw him, and he even went to see a chiropractor. Anita's worried, however, that the back problem is merely an excuse for her husband to become a shiftless bum. "His buddies from work don't even come by anymore. They think he's a malingerer." I don't know -- if he can't even make it down to the corner bar to see them, it's probably pretty serious. Peggy produces a copy of the new Horatio Hornblower she checked out of the library for Gerry, and then the doorbell rings, and it's Father Gill come to check on his bedridden parishioner. Anita goes to see if he's awake, leaving Father Gill open to mention that he thinks Peggy doesn't seem very comfortable at church. She unconvincingly denies that, but considering that the times we've seen her, it looks like she's been digging her nails into the pews for dear life, I'm going to have to agree. He tells her there are many ways she could be involved, and one of them would be helping out the committee for the CYO (Church Youth Organization?) dance with some publicity ideas. She tells him she's very busy, but he suggests asking her boss if she could do it pro bono, as he'd really like to see the kids show up this time. Anita returns and tells Father Gill that Gerry's ready to see him, so he leaves Peggy to contemplate if there's any way God will let her out of this one.