Cha-Ka is busy sweeping the dirt off the Temple's patio (or rather under it, since he peeks around and then sweeps the dust under a lifted tile) when he is startled by a smoking hot-air balloon crashing down into the nearby jungle. The frantic Paku quickly informs Uncle Jack, and when Jack sees the rising smoke, he dashes off to investigate.

Soon arriving at the crash site, Jack is greeted by a large, husky man wearing an early 20th century flying outfit and whistling "Yankee Doodle Dandy". The waxed-mustachioed man cheerfully asks Jack his name, then introduces himself as Colonel Roscoe T. Post. Colonel Post relates his story of trying to make the first solo balloon flight over the Andes when he encountered a violent storm with much lightning and great turbulence. At Jack's request, the Colonel reveals that he set out on March 3, 1920 ("a day to be marked by history!", he claims quite accurately). At the Colonel's request, Jack informs him that he has crashed in the "Land of the Lost"; the newly arrived Colonel considers the name "colorful", unaware of where he really is. Uncle Jack invites the Colonel back to the Temple, and as they stroll along, the guest brags about going over Niagara Falls in a barrel. The two men stop to avoid Grumpy roaring madly in a nearby clearing; Jack successfully distracts the beast by catapulting to the far side of the clearing a large rock using a flexible sapling. The Colonel is quite shaken by their meeting with the tyrannosaur, and insists on repairing his balloon to leave the valley as soon as possible. Uncle Jack informs his guest that he will need some help to repair the balloon, and offers the Marshall's assistance if they can ride along on the journey.

Back at the Temple, Will and Holly are ecstatic about the possibility of flying out of the Land of the Lost. (Why is it that during the third season the Marshalls seem to forget that they have it a little harder than Gilligan and his pals? The valley is a small, closed universe; they can only escape by passing through a time doorway.) The Colonel reminds the kids that there is much work to be done: inspect the hydrogen cylinders, repair the gondola, and most difficult of all, construct a new air bag. Holly proposes that they use reptile egg membranes for the balloon; Will adds that they are "light as a feather and tough as leather", while Jack notes that they are in plentiful supply. Everyone is excited about their upcoming journey, when just then Cha-Ka returns with an armful of firewood. The Paku cowers back, asking "who man?" in a nervous voice; the Colonel is awed by the fact that Cha-Ka speaks. Holly innocently introduces their Paku friend to their guest; the Colonel smiles sinisterly while he mutters "the missing link... my fortune is made!"

In the Library of Skulls, the Sleestak Leader addresses the Voice of Wisdom; two other Sleestak each rhythmically clunk small bone hammers against human skulls. The Leader reports to the Voice of Wisdom that another intruder has entered their land: a human descending from the heavens in a flaming machine. The Leader points out that the Sleestak are frightened, and seeks to know from the Skull if the intruder is an evil god. The Voice assures the Leader that "he is a god as one who wishes to be a god is a god; in the same way, he is evil." When the Leader asks if the intruder means them harm, the Voice replies "he does most harm who first harms himself". The Skull goes on to inform the Leader that to protect themselves from the intruder's power, they must destroy his machine. The Leader heeds the Voice's advice and gathers his warriors to plan the assault.

Outside the Temple, as the Marshalls gather around the gondola, the Colonel announces that the hydrogen cylinders are in fine working order and will provide enough lift to transport them all out of the valley. When Cha-Ka excitedly asks if he can fly too, the Colonel slyly replies that he wouldn't leave the Paku behind "for a million dollars". Uncle Jack takes charge by dividing the group into teams: he and his nephew will work on the gondola while Holly and Cha-Ka gather egg membranes with the Colonel. After Holly leads the Paku and their guest out into the jungle, Will asks his uncle to what time they will go when they escape. Jack at first considers any time better than the one they're in, but Will brings to his uncle's attention that they are not yet born in the Colonel's time. After a moment of pondering the possible consequences of returning to such a time, Jack decides that the family will concern themselves with the dilemma of times once they are actually on their way out of the valley.

Holly shows the Colonel the plaza of the Lost City. She claims that the Sleestak built it (wrong, the Sleestaks' ancestors did), and then goes on to depict the creatures as "kind of a cross between a giant lizard, a crab and a human". Cha-Ka informs their concerned guest that the Sleestak live underground; Holly adds that the creatures can no longer stand the light and heat of day. She advises the Colonel to consider himself lucky if he never has the opportunity to meet one. Heading over to the egg shells, they run into Big Alice; Holly assures their guest that her "bark is worse than her bite". The Colonel lags behind as they dash over to the shells (this was necessary for the video tape editors to reuse a Big Alice animation clip [The Search]). When they reach the giant egg shells, the Colonel hopes that the mother bird is long gone; Holly playfully corrects him by noting that they hatched from a brontosaurus. Holly surveys the surrounding area, spotting hundreds of shells, so they begin their work removing the strong, translucent membranes.

Back at the Temple courtyard, the Colonel oversees the Marshalls working, standing along the sidelines chuckling "splendid!" to himself. Inside the Temple after that evening's dinner, while the Marshalls soak the dishes, the Colonel reports that his inspection shows all of the equipment in fine working order: the pitch has completely sealed the airbag's seams, the gondola is sturdier than ever, and the ropes are strong and pliable. When the Colonel follows by announcing that they will embark on their journey first thing in the morning, the kids express their joy at leaving behind the creatures of their harsh Land; Holly says "no more Grumpy", while Will bids "so long, LuLu". Jack hears hissing outside, so he yells "Sleestak"; Will thinks his uncle is adding another member to their list! Will adds "goodbye, Sleestak" but his uncle corrects him by saying "no, I mean Sleestak!" and handing him a torch. While Will and Uncle Jack attempt to drive three of the creatures back into the jungle, the Colonel, standing in the Temple doorway, cries "Stop!" and charges out across the courtyard. The next scene is quite humorous, though it is one of the most pathetically staged Sleestak scenes: the Colonel screams for help as he struggles fruitlessly to free himself from the grip of one Sleestak while two others fumble to tear up the egg-membrane balloon. (What makes this scene really tacky is that the video editors sloppily left in some leading footage, so for a brief moment they all stand still before suddenly commencing action). Jack and Will come to their guest's rescue and drive off the sluggish Sleestak who stumble over the membranes as they escape into the jungle. The Colonel is discouraged that the "filthy beasts" destroyed their balloon, but Uncle Jack points out that it is only a delay; they have built one balloon, so they can simply build another. Will assures the Colonel of their determination, stating that "the Marshall family's gonna get out of the Land of the Lost!"

The next day while Holly and Cha-Ka gather more egg membranes, the Colonel tempts the young Paku with the promise of taking him around the world -- Europe, South America, and the mysterious Orient. He goes on to mention people they'll meet -- kings, emperors tycoons -- amazing technology they'll encounter -- powerful steam engine locomotives, tall skyscrapers, and speedy 40-mile-per hour automobiles -- great cities they'll visit -- Paris, London, New York -- and the wonderful social scene they'll enjoy -- stores, restaurants, and especially stage shows. Cha-Ka is most interested in meeting other Pakuni in these great cities, but the Colonel focuses on the stage shows, claiming that people will pay thousands of dollars to see Cha-Ka in one. "Colonel Roscoe T. Post presents for the world... The Missing Link!", he boasts to the Paku while Holly, off to the side, listens in on his money-making plan.

Back at the Temple, Holly tattles to her uncle, who is repairing the gondola, about the Colonel's plan to bring along Cha-Ka in order to become wealthy by exploiting the Paku like a freak. When Holly quotes their guest as calling Cha-Ka "the missing link", Uncle Jack decides to have a personal talk with the Colonel. Just then Will returns from the jungle with more vines; he reports that he discovered some fresh Pakuni tracks. Jack and Holly are hopeful that they can find other Pakuni so that they can reunite Cha-Ka with others of his own kind before they leave. Uncle Jack instructs Holly to start patching together the egg membranes, and when Cha-Ka and the Colonel return, begin sealing the seams; he and Will set out into the jungle to track down the other Pakuni.

The Colonel supervises Holly and Cha-Ka brushing sealer on the patched membranes when Will and Jack return early from their Pakuni hunt; the men explain that they simply followed the tracks until they came to a sheer cliff. Cha-Ka is at first discouraged, but then points out the Colonel's promise to take him to a great Pakuni city; their visitor waffles awkwardly in an attempt to play it down. Uncle Jack asks the kids and Cha-Ka to start preparing dinner so that he may have a moment alone to discuss the matter with their guest. Jack points out that they do not wish to leave Cha-Ka behind without fellow Pakuni, so they feel it is best to take him along. Jack lets their guest know that he has heard about the plans to exhibit the Paku as a freak for financial gain. The Colonel fumbles in his own defense, claiming that his intentions have been mistaken, that his goals are scientific and that his motives are purely altruistic. Uncle Jack remains unconvinced of the Colonel's claims, so he clearly warns their guest that he will do everything in his power to ensure Cha-ka's happy existence. The Colonel tries to further his host that the accusation is unfounded, but Uncle Jack walks off, leaving the Colonel fretting that his scheme appears to be foiled.

After supper, the men load the hydrogen cylinders into the gondola when Torchy approaches the courtyard to harass them. Will is concerned that the creature will burn the airbag, but the Colonel points out that the lizard's fire-breath could explode the hydrogen cylinders! Jack decides to teach Torchy a lesson, so he grabs a cylinder, runs over to the beast, releases some gas around it, and then runs for cover. He quickly explains to the others that the gas will surround Torchy and ignite in a huge burst when the creature lights up. Torchy blasts his breath, igniting the gas to create a giant fireball; the unexpected explosion sends the startled beast fleeing. The Colonel compliments Uncle Jack on his courage and ingenuity, but also brags that had he been closer to the cylinders he would have done the very same thing. The equipment appears to be in proper working order, so Jack proposes that they get to bed early in preparation for the their journey. To ward off anymore unexpected visitors, Jack also proposes that they hold a night watch: he assigns Will to the first shift, himself to the second, and gives the last shift to the Colonel.

Will is nodding off by the end of his shift, and is quite startled when his uncle comes to replace him. Jack fares better but still starts drifting off slightly by the time the Colonel comes for the final watch. As soon as Uncle Jack has retired in the Temple, the Colonel hastily puts on his scarf and pulls out his map. Cha-Ka wanders out into the courtyard, startling the Colonel; the Paku attributes his insominia to his anticipation of the fantastic journey ahead. The Colonel still plans to exhibit the Paku, asking him "are you ready to see the world? the world is ready to see you!" Cha-Ka demonstrates an exploding light crystal by tossing it out in front of him (why doesn't it wake the Marshalls, especially Uncle Jack, who has just retired?) Cha-Ka notes that it is almost dawn, so the Colonel starts filling the balloon with hydrogen gas from the tanks.Soon the balloon is filled, floating just above the ground; ropes tied to stakes keep it anchored to the earth. When the Colonel begins untying the ropes, Cha-Ka begins to panic; though the Colonel claims that they will only take the balloon up a few feet for a test flight, Cha-Ka still resists, screaming for the Marshalls to come and save him. The Colonel tries desperately to quiet the terror-stricken Paku; while covering the boy's mouth he whispers to the Cha-Ka that there is only enough gas to fly two passengers. Unfortunately for the Colonel, The Marshalls heard Cha-Ka's screams, and they dash out of the Temple to grab hold of the last rope. The Colonel commands the family to release the balloon, announcing that the remaining hydrogen cannot possibly fly them all out. Jack demands that the Colonel release captive Cha-Ka; the Pakuni boy repeats his plea to stay behind with the Marshalls. Will threatens to keep hold of the rope until Torchy comes back, so the Colonel frantically adjusts the gas to lower (?) the balloon down. Cha-Ka makes his escape by sliding down the rope, after which the Marshalls release it, letting the balloon fly free. Once the family calms Cha-Ka, he feels proud to be the "only Pakuni to fly in sky". Jack salutes the Colonel, who bids the Marshalls goodbye with a cheesy smile as if he is reveling in having taken the family for suckers. Will and Holly wonder where the Colonel could possibly be headed (where can he go in this small, closed universe? how likely is it that he will encounter another time doorway?); their uncle can only reply that the hot-air artist is in for alot of adventure.