The McCarthyism episode, which won a Writers Guild Award.
A congressional aide, Williamson (Lawrence Pressman), turns up at the 4077th. The gang wonders what he's up to as he goes around asking suspicious questions and insinuating that someone might not be pulling their weight. Eventually, he admits that he's investigating Margaret, whom he believes to be a communist sympathizer. It turns out an old college boyfriend of hers, Wally Chrichton, was a communist and now Williamson wants her to name their associates. Not wanting to put her old college friends through the wringer, Margaret considers resigning. Williamson goes to Margaret's tent and offers to let her off the hook in exchange for her sleeping with him. They're photographed kissing by Klinger, who had been trying to get a picture into Stars and Stripes as part of some apparently funny subplot, and the gang blackmails Williamson into silence. In The Tag, the gang learns that Williamson's wife was caught in an affair with the congressman he works for.
Attention, all personnel! Are you now or have you ever associated with the following tropes?
- Armor-Piercing Response: When Williamson talks about how America is under threat from the "Red menace", Hawkeye proceeds to tell him that the MASH is up to their ankles in the "Red menace", and that "It comes out of those kids you keep sending us", which visibly angers Williamson.
- Hauled Before a Senate Subcommittee: Williamson threatens Margaret with this. He doesn't mention HUAC by name, but it's presumably what he's talking about.
- Hypocrite: Williamson, who tries to force Margaret to have sex with him to overlook her supposed Communist sympathies, and when confronted claims that the gang threatening to send the photos to his wife is blackmail, which Margaret points out. Turns into Not Helping Your Case when he retorts that even if she had had sex with him he wouldn't have let her off the hook.
- Ironic Echo: When he arrives at the camp, Williamson brags about being married to his country first and his wife second. During The Tag, the justification Williamson's wife gives in the paper for cheating on him was that she wanted a man who wasn't married to his job first and his wife second. Ditto his remark about having the Congressman's ear, to which Margaret would ultimately reply that his wife "got everything else".
- Mathematician's Answer: When Williamson tries to seduce Margaret and Klinger gets a snapshot of it:Williamson: Wh-what's he doing with that camera?
Charles: He appears to be rewinding. - Pun: Klinger, envisioning the headline he thinks he'll get for catching Williamson assaulting Margaret on film: "VIP Makes Major Mistake!"
- Red Scare: The whole point of the episode. It's pretty accurate about the climate of the McCarthy era (hence Williamson's assertion that Communists have supposedly infiltrated the "highest levels" of the government, a similar claim that McCarthy often made), when you could indeed be ruined just for appearing before HUAC, whether you were found guilty or not.
- Scarpia Ultimatum: Williamson hints that he'll let Margaret go in exchange for a night together. Ultimately subverted; he had no intention of letting her go whether she slept with him or not.
- Trailers Always Spoil: According to Rappaport, the first act was supposed to have everyone thinking Hawkeye (who had his own version with Flagg last season anyway) was the one being investigated before The Reveal that it was Margaret. The trailers ran "Margaret Houlihan a commie?", spoiling the whole thing.
- Smug Snake: Williamson, whose stuck up attitude rubs everyone the wrong way.
