In the middle of the night, a bunch of combat engineers are brought into camp. After treating them, the major staff gathers in the mess hall. Charles, who is suffering from a toothache but won't admit it, goes back to the SWAMP. At the same time, a Major named Weems arrives at the camp. Weems is the commander of the men who were brought in, and came to see them. The camp immediately like him, and Hawkeye and Bj offer him a cot in the SWAMP.
The next day, Charles starts looking for anything that will help kill the pain he is in, even resorting to stealing from supplies and going to a native healer. It turns our that Charles won;t admit he's having tooth problems because he doesn't want to see a dentist. Meanwhile, Weems visits his men in Post Op. While there, he promises one of his men, Dorsey, that he is being sent home because of his wounds. Hawkeye pulls him aside and tells him Dorsey won't be because he isn't that heavily wounded. But another man in Weems' unit is that heavily wounded, and Weems wants to keep him. Weems eventually tells Hawkeye that Dorsey comes from a poor family and that his parents are struggling to keep their farm working without him. Hawkeye decides to try to get Dorsey a hardship discharge. However, Hawkeye later finds out Dorsey is from Brooklyn, which is no where near any farms. He questions Dorsey, who turns his back on him when he finds out he was talking to Weems.
Hawkeye is perplexed about all this, and tells Bj about it. When Bj points out that Dorsey is black and the boy Weems wanted to keep is white, Hawkeye is even more confused; in his opinion, sending anyone home is the best thing that can happen to them, so he doesn't think Weems can be racist. But more black people from Weems' unit arrive, prompting them to investigate. Hawkeye, Bj, and Klinger eventually uncover that in Weems unit, black people suffer 46% of the casualties, despite only making up 11% of the entire unit.
After reporting this to Col.Potter, they stage a trap for Weems. Hawkeye and Bj hold a drinking party outside the SWAMP that Weems and Potter attemd. While talking, Potter starts talking racial bigotry, luring Weems into a false sense of security. Weems admits that he was upset when the President desegrgated the troops, and that he doesn't want any black people in his unit. Therefore, he sends those black people in his unit on high risk duty so they get more points and get rotated home faster, or get wounded.
Col.Potter then invites the others into the Swamp for a drink, where Weems finds out their entire conversation was overheard by Charles and Quentin Rockingham, a black man who is also an Army major and a representative of I-Corps. Rockingham is disgusted with Weems' racial attitude, and gives him two choices. Rockingham tells Weems that he can either resign his commission there and then, or he will place a call to the Judge Advocate General and have him court-martialed. Cornered, Weems resigns his commission and bitterly leaves, claiming you used to be able to know who your enemy was.
After he does, Col. Potter reveals to a stunned Hawkeye and B.J. that the entire thing was just a ruse to get Weems to resign his commission, with Charles willingly participating. Charles lent Rockingham, a captain within the MASH system, his gold clusters so he could portray a major. The ruse worked perfectly, but unbeknownst to Charles there was another reason why Captain Rockingham was called to the 4077th. Hawkeye, B.J., and Col. Potter reveal that not only is the captain a practicing doctor, he is also a dentist- meaning that Charles is going to have to face his toothache one way or the other.
The last scene is of the medical staff gathered around Rockingham, who has bitten in the hand by Charles during his operation.