Frank Burns cracks up over Margaret's marriage while on R&R in Tokyo, and Major Charles Emerson Winchester III is sent to the 4077th as a replacement by a vindictive superior officer.

Madness strikes as B.J. and his old friend Bardonaro play a series of practical jokes on each other, just as Bardonaro is about to leave Korea. Hawkeye gets the last laugh. He sends Bardonaro off without his traveling papers, and in a jeep with too little gas.

The 4077th, caught up in tension and nerves, creates a bonfire to release their pressure. Meanwhile, Sidney Freedman is depressed over a young soldier who blames him for his injuries, because Freedman had sent him back into combat.

Hawkeye tries unsuccessfully to get to Seoul, to see Nurse Gilmore for the weekend. Meanwhile, Winchester has taped a letter home, asking for his influential parents to help get him back to the States. To get even, Hawkeye and B.J. switch Winchester's clothes, causing Winchester to alter his eating patterns.

With supplies low, the 4077th gets a truckload of ice cream churns and salt tablets. But what it needs are light bulbs, and in the dimly lit post-op Charles makes an error for which he draws the ultimate wrath of his two surgeon bunkmates. Meanwhile, B.J. receives a mystery novel that everyone in camp reads in turn. The last page is missing and the solution to the mystery is undiscovered until B.J. calls the author by long distance.

Hawkeye falls in love with Kyong Soon, a Korean woman who is caring for her sick mother and orphaned children. But all hope is lost as Kyong takes her possessions and the children to the south after her mother has died.

Charles plans a scheme to get rich when he discovers that blue scrip is going to be exchanged for red. Hawkeye and B.J. outsmart him, and he is left holding the worthless scrip. Klinger tries to get into West Point so that he can get out of Korea.

Radar notices a number of tattoos on one of the wounded, and convinces himself that with a tattoo he will be irresistible to women. Everyone tries to discourage him, and he admits to having received a tattoo that will wash off. Meanwhile, Margaret is frustrated with a new nurse who keeps getting upset at the sight of combat injuries.

Colonel Potter, deciding that the camp is out of shape, enforces a calisthenics course. When nobody is enjoying it, he makes it fun by splitting the camp into two teams. These teams compete for three day R&R passes. Klinger tries to get out of the army by getting fat.

Colonel Bloodworth threatens to press court-martial charges against Hawkeye, who shoved him in the bar. But then he becomes a patient and witnesses Hawkeye's skills. Klinger bonds with a patient from his hometown.

Lost behind enemy lines, Hawkeye and Margaret form a personal truce and seek shelter in a roadside hut.

B.J. disobeys orders and goes out to find Hawkeye and Margret, who are still missing in action. Meanwhile, their romantic relationship quickly goes up in flames, and they become even more hostile toward each other.

After Charles hands B.J. two hundred dollars, he begins to take advantage. Everyone gets together and persuades Charles to play poker. He has incredible beginner's luck until Radar discovers that Charles whistles loudly when he bluffs. They all win back their money and then some.

Hawkeye and B.J. refuse to shower until Charles stops playing his French horn, and Colonel Potter deals with a patient who wants to kill himself because he is now disfigured.

In need of a special surgical clamp, Hawkeye and B.J. hire Mr. Shin, a local jewelry dealer, to make it. Days later the clamp is used to save the leg of a wounded soldier. Mr. Shin goes into the surgical supply business.

With British and American casualties heavy, the 4077th's supply of penicillin has been stolen. Father Mulcahy discovers, from Corporal Bryant, the location of some penicillin, and he and Klinger go out in search of it. They are shot at, but safely return with the drug and save the day.

With the arrival of a shipment of records, Radar plays the part of a disc jockey and helps to get everyone through the incredibly long deluge of wounded.

Hot Lips, believing herself to be pregnant, asks Hawkeye to test her. The only rabbit available to use for the test is Radar's pet, Fluffy. Meanwhile, Martinson, a patient, holds Charles at gunpoint, demanding he be sent back to Ohio.

After a delay of three weeks, five sacks of mail arrive, and everyone in camp reacts to good and bad news from home. Hawkeye receives love letters addressed to another Benjamin Pierce, another man has approached B.J.'s wife, and Radar's mom has found a boyfriend. Klinger: "I may not have a family in Toledo, but I got one here."

With a temporary transfer of personnel between the 4077th and the 8063rd, Captain Roy Dupree replaces Hawkeye, whilst Lorraine Anderson makes eyes at Charles. Fearing this to be permanent, Charles and B.J. successfully conspire to have Dupree permanently removed from the 4077th. Charles (to Hawkeye): "God, I missed you!"

When bad reports are filed at headquarters, Col. Potter contemplates retirement.

Charles takes amphetamines to keep up his energy level, and even drugs Radar's mouse, "Daisy", so that it will win a race against a Marine's mouse, "Sluggo".

The doctors have to deal with a short supply of morphine and too many patients, while Klinger has to deal with a corporal who may be crazier than he is.