When Charles mocks a news story about a Time Capsule being buried in the cornerstone of a new Los Angeles skyscraper, Margaret gets the idea to bury a time capsule from the 4077 staff in the compound, containing mementoes of who they were and why they were there. Hawkeye volunteers to assist, much to the surprise of his bunkmates and the scepticism of the major, but he allays the former and confirms the latter by treating the project as cynically as possible until Margaret fires him... whereupon Hawkeye puts together his own, joke time capsule filled with inappropriate items, further stoking her rage.
Meanwhile, just as Father Mulcahy is seeing off a group of refugees, including a farmer and his wife who have lost track of their daughter, a new batch of wounded arrive, among them a female Korean prisoner named Soon-Lee, who is accused of sniping at American troops after she was found with a (US Army) rifle. However, the sniper victim, a Corporal Stoddard, was put on a chopper that still hasn't arrived despite having left hours earlier, and as they haven't made radio contact either, Colonel Potter has them listed as MIA. Klinger is assigned to guard Soon-Lee until she can be interrogated by the Korean police, but she insists that she's innocent and begs to be allowed to find her parents; Mulcahy, assuming that she's the refugee couple's daughter, tells her he knows where they are, but that they'll have to move on again in a day.
In a comic subplot, Rizzo borrows a dummy hand grenade Igor was planning to convert into a reading lamp for a revenge prank on B.J., after the latter rouses him from one of his many naps by asking if "the general's jeep" is ready. Rizzo brings the grenade into the shower, "accidentally" pulls the pin, and flees the tent with the nude captain before revealing the ruse. Later, in the mess tent, Charles bumps into Rizzo and blames him for the collision, so Rizzo attempts to repeat the prank when he shows up to the Swamp to (pretend to) apologise... only for Charles to throw himself on the grenade. When it doesn't go off, Charles declares it a miracle and tells Rizzo he'll dispose of the "dud" grenade safely... before giving an "OK" sign to B.J., who is hiding outside the tent.
When the chopper carrying Stoddard finally arrives, the pilot, Lt. Brannum, explains to Col. Potter that they were shot at by North Korean snipers, and two bullets severed the fan belt and broke the radio tubes. Brannum asks for a new fan belt and takes off again, but not before mentioning to Klinger that Stoddard was shot by a sniper. At Klinger's request, B.J. gives him the bullet from Stoddard's body, which doesn't match the gun Soon-Lee was found holding and exonerates her. Father Mulcahy rushes her to the refugee camp... but she isn't the daughter of the farming couple after all, so their searches go on. As for Stoddard, as he is recovering in Post Op, he tells an awed Hawkeye and Margaret that Brannum had to make the journey to the 4077th in 200-yard hops, scouting ahead for a clearing in which to make a safe landing while the engine cooled off each time, and keeping the corporal warm with a blanket when it was too dark to fly.
As Margaret buries her time capsule, she is incensed when Hawkeye arrives with his own capsule... until he reveals that it includes Brannum's broken fan belt, as a symbol of the Humble Heroes who did so much and asked for so little in return; Radar O'Reilly's teddy bear, a symbol of soldiers who came to Korea as boys and went home as men; a fishing lure that once belonged to Henry Blake, a symbol of soldiers who never made it home; and a pair of boxing gloves from Father Mulcahy, who hopes that nations will use them to settle their differences instead of guns.
In The Tag, Klinger and Soon-Lee, who have grown close in their time together, join the Swampmen for a drink in the Officers' Club – until they see the huge crowd waiting to get in. No problem, says Charles, producing the dummy grenade...
Attention, all personnel! We submit the following tropes for inclusion in Major Houlihan's time capsule:
- Bait-and-Switch: In a sad use of this trope, when Father Mulcahy learns that Soon-Lee was separated from her parents while fleeing an attack on her village, he assumes she is the daughter of the farmer and his wife who were loaded onto the refugee truck in the first act. He brings Soon Lee to the refugee camp, finds the farmer and his wife, and joyfully announces that he found their daughter... but the sorrowful expressions on their faces make it clear that she's not their daughter after all.
- Batman Gambit: B.J. enlists Charles' help to get revenge on Rizzo for the "dummy grenade in the shower tent" prank, so the major bumps into Rizzo in the mess tent and acts as though it's the sergeant's fault, following up the collision with a few insults. As expected, Rizzo tries to get revenge with a second iteration of his earlier prank, but Charles is ready for him and puts a definitive end to the grenade pranks.
- Clear Their Name: Though Klinger is initially cold toward Soon-Lee, he thaws out when he sees how desperate she is to be re-united with her parents, and he finds himself doubting that she could be the sniper who shot Stoddard. When Stoddard finally arrives at the 4077th, Klinger asks B.J. to give him the bullet, which is not a match for the gun Soon-Lee was holding when she was arrested, proving her innocence.
- Continuity Nod: Several characters who had long since departed the series are referenced in the time capsule scene. The contents include Radar's teddy bear, left behind in his farewell episode "Good-Bye, Radar"; one of the many fishing lures that used to adorn the late Henry Blake's hat, which B.J. says he used a few times; and Klinger's Scarlett O'Hara gown, from his old Section 8 seeking days. Later, Charles notes that they included nothing from Frank Burns; Hawkeye jokes that they thought about putting in his scalpel, but decided against burying deadly weapons.
- Due to the Dead: B.J.'s contribution to the time capsule is the late Henry Blake's fishing lure as a tribute to those that died during the war.
- End-of-Series Awareness: While not the actual finale, it was the last episode filmed as the last half-hour episode. As a result, it is the last one shown in the syndicated reruns package. Margaret's Time Capsule plot reflects how the end is near, as she insists the group do something to acknowledge how they were all there and prevent their work from being forgotten. Former series regulars Radar, Henry Blake, and even Frank Burns get referenced, as well as the long-since-discontinued Running Gag of Klinger's Section 8 antics.
- Fake in the Hole: Rizzo pretends the fake grenade he borrowed from Igor is live when he "accidentally" pulls the pin out in the shower tent with B.J. and in the Swamp with Charles; the difference is that B.J. doesn't know the grenade is a fake, but Charles does (having been told by B.J.).
- Food Slap: When Father Mulcahy tells Soon-Lee that he met a farmer and his wife who were separated from their daughter when their village was attacked, she assumes they were her parents and begs to be released, especially when Mulcahy says they'll only be able to stay at the UN refugee camp for a day, but Klinger won't let her go. She hurls her tray of food at him in despair and anger.
- Foreign Queasine: When Rizzo thanks Charles for "saving" him from the (dud) grenade, he says that if the major comes to Louisiana, his wife Zola will cook up the biggest plate of pig's feet he ever saw. Charles, choking back bile, says his mouth is watering at the prospect.
- Four Lines, All Waiting: The episode cuts back and forth between the plot threads of Margaret's Time Capsule, the whereabouts of the chopper carrying the wounded Corporal Stoddard, Rizzo's pranks with the dummy hand grenade, and Soon Lee's search for her parents.
- Humble Hero: Corporal Stoddard tells Hawkeye and Margaret that Lt. Brannum, the chopper pilot who flew him to the 4077th, had to make the journey 200 yards at a time as his engine kept overheating thanks to a broken fan belt, so he landed, scouted ahead for the next safe landing place, and then returned, by which time the engine was cool enough to take off again. When night fell and they couldn't fly, Brannum kept Stoddard warm with a blanket until dawn, when they took off again. But Brannum doesn't so much as mention this to the doctors; he simply gets a new fan belt and takes off again. To him, saving Stoddard is all part of the job and the complications that arose were just inconveniences to be overcome.
- Ironic Echo: When B.J. wakes a napping Rizzo in the Officer's Club by asking if "the general's jeep" is ready, he tells the unamused motor pool sergeant, "It's just a joke!" Later, when Rizzo uses the dummy grenade he borrowed from Igor to fool a nude B.J. into fleeing the shower tent, he tells the incensed surgeon, "It's just a joke!"
- Jumping on a Grenade: When Rizzo tries to prank Charles with the dummy grenade with which he has already pranked B.J., he is stunned when the major throws himself on the grenade after he "accidentally" pulls out the pin and yells, "Save yourself!" It emerges that Charles knew all along that the grenade was a fake, having conspired with B.J. to counterprank Rizzo.
- Not So Above It All: When the others doubt they'll be able to get a table, Charles knows how to clear some space and reveals he still has the fake grenade.
- Oh, Crap!: First B.J., then Charles get looks of panic when Rizzo produces the dummy grenade in front of them and "accidentally" pulls out the pin.
- Sure, Let's Go with That: When Rizzo expresses amazement that Charles was apparently willing to sacrifice his life by throwing himself on the "dud" grenade, Charles modestly says it's nothing Rizzo wouldn't have done for him. Rizzo agrees, though he and Charles both know this to be a lie.
- The Tag: As Charles muses to his bunkmates that the time capsule didn't include anything from Frank Burns, Klinger and Soon-Lee join them for a drink at the Officers' Club, but there's already a huge crowd inside and outside. Charles says he expects a few tables to open up and produces the fake hand grenade.
- Time Capsule: One of the main plot threads of this episode sees Margaret planning to bury a time capsule containing memorabilia from the staff of the 4077th to symbolise what they have been doing in Korea, such as a duty roster or a nurse's manual; Hawkeye angers her with a more cynical take, especially when he suggests Col. Potter include a pack of bunion pads, that Charles include a cheap bottle of cognac, and that Klinger include one of his dresses. Ultimately, Margaret ends up including the cognac and one of Klinger's dresses anyway.
