At the 4077th Mobile Army Surgical Hospital (M.A.S.H) unit in Korea, two army doctors by the names of Hawkeye Pierce and Trapper John McIntyre receive some exciting news in the mail. Their Korean house boy, Ho-John got accepted into Hawkeye's old college. Hawkeye and Trapper decide to hold a party filled with music, dancing, and alcohol to raise money for Ho-John's plane trip to the U.S. They achieve this by raffling off a weekend pass with a nurse, Lieutenant Dish for R&R in Tokyo.

Hawkeye writes home, describing Christmas in Korea: Radar ships a jeep home, a piece at a time; Henry gives the monthly lecture on sex, with the aid of figure A and figure B; Trapper helps deliver a calf; Klinger and Frank get into a fight, but Father Mulcahy smoothes things over; Hawkeye and Trapper sabotage Margaret's tent; Hawkeye flies to the front line dressed as Santa, to help a wounded soldier.

The camp tunes into the Army/Navy football game, only to be shelled and have an unexploded bomb land in the middle of the compound. They ring around trying to identify the bomb, and the camp prepares for the worst. Hawkeye and Trapper are left the task of following instructions to disarm the bomb, which turns out to be full of propaganda leaflets from the CIA.

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.

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 OR is filled with more wounded than the unit can handle. Hawkeye does heart massage on a soldier, which saves his life, but he dies four hours later. Sidney Freedman drops in during the deluge, and is dragged into the fray by Hawkeye.

Sick and tired of having liver and fish for an 11-day stretch, Hawkeye, driven near to insanity, starts a riot in the mess tent. He and Trapper then orders spare ribs and sauce from the best place he ever had them, in Chicago. Trapper calls a woman he spent a weekend with to pick up the ribs, and then they get choppered in. Unfortunately, right as they're sitting down to eat, wounded arrive, and Hawkeye is forced to postpone sinking his teeth into his beloved ribs.

Hawkeye records a letter to his dad, detailing the exploits of a mad Turkish soldier who calls Hawkeye a "damn good Joe," the unfortunate loss of the corpse of a Luxembourg soldier (who turns out not to be dead), Lt. Henri-Batiste LeClerc, and of a gun-happy officer.

Dr. Borelli visits the 4077th to demonstrate his artery transplant technique. Unfortunately, being so close to the front at the 4077th causes Borelli's drinking problem to interfere at the worst time - when a patient needs the transplant.

Trapper is shipped home while Hawkeye is on R&R. Hawkeye speeds to Kimpo with Radar to catch Trapper's plane, but they just miss him. While they are there, they pick up BJ Hunnicut and take him back to camp. On the way back, BJ is introduced to the Korean War.

Frank settles in as commanding officer, only to have a new one appointed over his head, one that, to his chagrin, fits in very well.

A freezing night, an artillery barrage that's coming too close, a patient going downhill, and Frank's searching Hot Lips' tent for his letters.

Radar is driving Hawk, B.J., Sherman, and Frank in a bus back from a "medical conference" when they get lost. They stop to see if they can find anything they recognize. When they decide to turn around, they find that the bus does not want to start. Radar goes off in the middle of the night for the latrine, and does not immediately return. Stricken, Hawkeye wants to set out to find him, only to be stopped by Sherman. An injured Korean surrenders to get medical help from Hawk and B.J.. Upon Radar return, the Korean helps repair the bus and get them out of danger.

Frank has a fever and makes a will, leaving all his money to his wife and all his clothes to Hot Lips.

Radar gets the help of Hawkeye and B.J. to procure something Colonel Potter says he's fond of, but that's hard to come by - tomato juice.

Potter decides Frank would be less of a pain if the others were friendlier to him; they oblige, with some startling results.

Hawkeye is reunited with a woman he thought was out of his life forever, but who never altogether leaves.

When a rumor for a camp relocation turns out to be real, Hawkeye, Margaret and Radar volunteer to stay behind for a patient who cannot be moved.

Hawkeye is temporarily blinded while trying to fix the nurses' furnace, and Frank finds a sure-fire way to win bets on baseball games.

Margaret takes off in the middle of the night to help deliver a Korean baby. Nobody knows of her whereabouts, and Colonel Flagg is brought in to help investigate her disappearance.

Instead of turning him in as a prisoner of war, Hawkeye and B.J. pull some strings to get a wounded North Korean surgeon a spot on the staff.

B.J. falls off the fidelity wagon while trying to provide consolation to a nurse whose marriage has just ended. But will he confess his infidelity to his wife?

The 4077th is deluged with patients and their individual medical histories. Then they run out of blood and everyone is donating at 48-hour intervals.

Pressured by Frank, Margaret decides to marry Colonel Donald Penobscott at the 4077th. When Donald arrives in camp, he is treated to a bachelor party and a practical joke while the nurses give Margaret a bridal shower.