After Maj. Margaret Houlihan-Penobscott leaves for her honeymoon, Maj. Frank Burns becomes very distraught, so Potter sends him on R&R. As they deal with the physical and psychological wounds in a heavy load of casualties, members of the 4077th wonder why Maj. Burns is late in returning from R&R and why Margaret returned from her honeymoon in a deep funk. Soon they learn that Maj. Burns has been arrested for antics with a general and his wife in Seoul; later, Hawkeye and BJ will discover that Margaret has already encountered marital troubles. Radar gets a temporary replacement for Maj. Burns: a Major Charles Emerson Winchester III. Maj. Winchester arrives at the 4077th, only to painfully discover that he's the permanent replacement after Frank Burns is thoroughly examined, uncannily acquitted, undeservingly promoted (to Lt. Colonel!!!), and quickly transferred to a VA hospital in Indiana.

Radar wants to become a man so Hawkeye recommends he goes to Seoul. On his way there he is hit by a mine. Hawkeye performs surgery on him. After surgery, Hawkeye goes to the Officers Club where he gets hammered. The next day he goes to surgery severely hung over. Radar tells Hawkeye he is disappointed in him. Hawkeye explodes and is then yelled at by Major Houlihan, Colonel Potter and Father Mulcahy. Radar and Hawkeye make up. Radar receives a Purple Heart.

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 Victor Bloodworth predicts that 280 wounded will arrive at the 4077th. Hawkeye is antagonized by Bloodworth and shoves him against a wall. Bloodworth presses for a court martial until he becomes one of the wounded and watches Hawkeye saving a soldier's life. Realizing Hawkeye's value as a doctor, Bloodworth drops all charges.

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

Margaret and Hawkeye seek solace from enemy fire in each other's arms and end up, briefly, as lovers.

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.

The 4077th has just ended a rough 3-day ordeal with wounded soldiers. Charles plays (?) a French horn and drives Hawkeye and B.J. crazy. They refuse to bathe until the French horn playing is stopped; the two are even forced to eat outside because of their unhygenic presences. Meanwhile Potter attempts to saves the life of a patient, Saunders, whose unfortunate accident has rendered him suicidal. Time and time again, Potter pleads against Saunders' taking the easy way out; Saunders holds out until a little dose of reverse psychology finally discourages him. When a "battle of the bands" eventually erupts between Winchester, Hunnicutt and Pierce, the camp collectively intervenes and hoses down Hawkeye and B.O. while Margaret has a soldier run over Charles' French horn with a jeep. Later, Sang Nu presents Charles with a new horn...one which doesn't have a mouthpiece!

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!"

Potter is upset when General Waldo Kent informs him that people in the 4077th are complaining about his leadership. Potter returns to camp and discovers that the complaints are coming from a Corporal (actually Lieutenant) Benson, who had been sent by a disturbed Colonel Frank Webster, who had been wounded some months earlier...and probably wanted payback for being made to wait until the real casualties were treated.

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".

With the possibility of contaminated morphine, the doctors at the 4077th administer placebos to the patients, which seems to work. Meanwhile, a new soldier, "Boots" Miller, is released on a Section Eight.