A Congressional aide named Williamson is on a visit to units in Korea, and stops at the 4077th. While there, he starts asking people questions. He starts with Margaret, then Hawkeye and Bj, Father Mulcahy, and Winchester.
Father Mulcahy mentions that he was uncomfortable with the questions he was asked, and Hawkeye and Bj, after talking about Williamson to Mulcahy and Margaret, become convinced he intends to cut the budget of their unit. They decide to confront him about this. After Hawkeye accuses him of planning to cut some of their key personnel, Williamson says they need to discuss the situation with Col.Potter. They go to Potter's tent, where Williamson says he's not there about budget cuts. He's there because he uncovered evidence that suggests on of the people in the unit is a communist sympathizer. This stuns everyone present, and when Potter asks who it is, Williamson says its Margaret.
Sometime later, Margaret, Potter, Hawkeye, Bj and Williamson meet in the CO's office. Margaret is shocked and deeply offended Williamson would even suspect her of sympathizing with the communists, let alone actually sympathizing with them. Williamson says he came to his conclusion because of her previous relationship with a man named Wally Crichton. He was labeled a communist by the House Committee, and Margaret's dating him has led to Williamson's accusation. Margaret claims there was nothing subversive about her relationship with Wally, and Williamson asks her to prove her loyalty by giving him the names of other people Wally associated with. When Hawkeye asks what will happen if Margaret doesn't cooperate, Williamson says he would arrange to have her testify before the Committee, which, whether she won or lost, would jeapordize her career. Bj tells Margaret not to give in, and Hawkeye furiously berrates Williamson, but he refuses to back down.
Hawkeye adn Bj later find Margaret in the mess tent. Margaret is distraught over her situation. After thinking about her old friends, she decides she can't tell Williamson about them because she doesn't want them to suffer. But when Hawkeye and Bj offer to help her fight Williamson, she reveals, to their horror, that she intends to resign her commission. Margaret says she can't afford to go before the committee because, whether she won or lost, she would be publically humiliated and it would bring unacceptable suffering to her father. Margaret then leaves the mess tent in tears.
Later that night, Hawkeye, Bj, and Winchester confront Williamson about his accusation. They defend Margaret, and Hawkeye, in the process, mentions her old nickname; Hotlips. Williamson becomes intrigued by this, and later meets Margaret in her tent. He says he'll help her fight the Committee, but they need to be "closer" before he can help her. After he says this, he throws himself on top of Margaret, who appears to accept it. But Klinger, who was hiding in Margaret's closet, captures this with a camera. Hawkeye, Bj and Winchester then burst in to reveal they had set Williamson up in order to get him to try to make a move on Margaret. They blackmail Williamson into letting Margaret completely alone, saying they'll send the pictures to his wife if he doesn't. Defeated, Williamson leaves.
Sometime later, the gang gets a huge laugh from something in Stars and Stripes: Williamson's wife was caught cheating on him with his boss.