Brought on by Frank and Margaret's negative reports, General Clayton assigns a psychiatrist, Captain Hildebrand, to examine the 4077th M*A*S*H unit, to see if it should be disbanded. Henry tells them to be on their best behavior, or else they will be split up. But the 4077th soon begins to act in their traditional, insane ways: the shrink experiences Max Klinger, watches the hijinks of Hawkeye and Trapper John, and witnesses the trysts of Frank and Hot Lips. While Hildebrand confronts the unit on its behaviour, choppers bearing wounded begin to arrive and everyone heads for the OR. The onslaught of casualties shows the 4077th's true side.

An inept North Korean pilot, known as "5 O'Clock Charlie", makes his daily attempt to bomb the ammo dump. Frank puts in a request for an anti-aircraft gun, which is granted when Charlie hits General Clayton's jeep. Frank takes charge of the gun, while Hawkeye and Trapper are determined to prevent him using it, by getting rid of the ammo dump. Frank misses Charlie and destroys the dump.

Radar writes the weekly activity report. Hawkeye operates on a wounded prisoner who grabs a scalpel and attacks the doctors. Frank wants Klinger thrown out on a section 8,so Henry calls in a psychiatrist, Major Freedman. Hawkeye is attracted to a new nurse but thinks she is married. Trapper loses a patient who developed complications during the O.R. fracas with the wounded soldier.

Hawkeye and Trapper want the army to admit responsibility for the accidental bombing of a local village. They fill out a report and Major Stoner arrives to investigate, and leaves with all the evidence. When the story is released it claims that the enemy bombed the village, and the army tries to gag the doctors. But, thinking there could be a medal in it for him, Frank has also put a report together, with copies of all the evidence, including shell fragments, so the army comes clean.

Hawkeye has been in non-stop surgery for 3 straight days without sleep, and the wounded keep coming. He decides to find out who started the war, and sends a telegram to Harry S Truman. After listening to some of Frank's rubbish about the North Koreans wanting better plumbing, he tries to send the officers' latrine to the North Koreans with an offer of peace. Trapper finally manages to sedate him. Trapper (about Hawkeye): "I guess he's just unstable. You see, he took this weird oath as a young man, never to just stand by and watch people die."

Hawkeye operates on a 5-year old Korean boy, and Radar can't find his family. Henry plans to send him to the orphanage, and the camp enjoys his company while they can. Trapper decides to adopt him after consulting his wife, and has to rescue him after he wanders into the minefield. Kim's mother turns up at the orphanage looking for him.

Corporal Walker is being sent home, and he wants to marry his Korean girl so she and their baby can return with him. CID sends Lt Willis to investigate, but when he refuses Hawkeye and Trapper frame him. Hawkeye is upset that a nurse he was pursuing does not approve of the marriage between "a gook" and "one of us".

Majors Houlihan and Burns press charges against Colonel Blake to get him arrested and put Frank in charge, and put Hawkeye and trapper under arrest so that they can't help him. Fortunately for Henry, they escape, and with the aid of Meg Cratty come to the rescue.

Once more Hawkeye writes home to his father: the doctors operate on a soldier with a grenade shot into his body; Hawkeye and Trapper colour the skin of a racist patient, who demanded the right colour blood, while he is asleep; Henry gets a movie of his daughters birthday from home; the officers hold the monthly staff meeting.

A lone sniper has the 4077th pinned down - including Radar and Henry in the shower. The poor boy thinks he's firing on McArthur's headquarters, and a chopper finally comes by and wounds him with gunfire from above, ending the siege. Hawkeye walks out to into the bush to tend to the wounded soldier.

The camp succumbs to the Asian flu, except for Hawkeye and Margaret, who have to do everything themselves. As the others start to recover, Hawkeye falls ill but he still manages to operate when wounded arrive. Finally the others are well enough for Hawkeye to stop working and rest. He is thanked for his service with a commemorative roll of toilet paper.

Hawkeye and Trapper recover from an all night party. Henry gets a barbecue, and Hawkeye puts in a request for an incubator. The Quartermaster turns him down. They locate a Major with 3 incubators, but he won't let them have one. A Colonel tries to sell them one, and then they get into trouble with a General at a press conference. Finally, Radar trades the barbecue for an incubator.

The 4077th and friends convene for their weekly “Medical Conference,” A.K.A. Poker while Radar runs over a civilian and Frank is held hostage in the showers by an enlisted man.

Hot Lips gets depressed and requests a transfer, causing turmoil in the camp.

Klinger pretends to be pregnant. Hawkeye and Trapper operate on General Mitchell's son, and the General gives them 3 days in Tokyo Henry keeps getting calls from Tokyo about what Hawkeye and Trapper are doing. When they get back to the 4077 Frank asked the general for an officers club for the camp. They plot to allow the enlisted men access to the club, and when the General opens it the rules are bent to give his son access, which Hawkeye exploits to give access to all.

Henry returns from a week in Tokyo, to announce that he is in love with a 20-year old girl called Nancy Sue Parker. She arrives for the weekend, and Henry shows her off. Nancy comes on to Hawkeye while Henry is in surgery. Henry is reminded of his wife back home when Radar places a call for him, and he realises it's his wife he loves.

A riotous episode in which Hawkeye will do anything to get a new pair of boots: In order to get Zale to get him some, he must get an appointment for Zale with Futterman, the camp dentist, who will only do it if Henry will give him a pass to Tokyo, and Henry will only grant the pass if Houlihan will get off his back, which she will do only if the guys throw a party for Frank's birthday, with a cake, and Radar will only help get the cake if he gets a date with Nurse Murphy, who will only date someone with a hair dryer, and Klinger won't give up the hair dryer unless he gets a section 8 (and Frank won't sign). Inevitably, the deal falls through, much to the Hawkeye's chagrin.

Private Baker, who is always going AWOL, is desperate for plastic surgery on his nose. Hawkeye gets an old friend, and plastic surgeon, to visit the camp, promising him a nurse called "The Barracuda". They put together an elaborate scheme to perform the operation without Frank or Margaret finding out.

A Korean family set up camp in the middle of the compound. A Korean woman with a baby comes looking for the father, and names Radar. Civilian affairs relocates the family and blood tests prove Radar is not the father.

The supply lines to the camp are cut. Radar, the housing officer, starts doubling people up to save fuel and Klinger is thrown out of the nurse's tent. People start burning everything to stay warm while Frank wears his heated socks. The toilet paper supply is worst hit, and then wounded start arriving. Supplies are eventually restored.

Burns tries to slap a dishonorable discharge on a decorated soldier who admits to being a homosexual, Private Weston. Weston: "Two guys got beaten up in my outfit. One colored, the other homosexual. As you can see, Doc., I'm not colored."

The arrival of a new batch of mail leaves Trapper depressed, and thinking of desertion, despite Hawkeye's efforts to dissuade him. Meanwhile, Hawkeye learns that he has successfully tricked Frank into buying stocks in a fictitious company, Pioneer Aviation.

Frank is investigated by two crazy intelligence men, one who's convinced he's a communist, the other's certain Frank's a fascist.