While Peter is strolling in the city playing his guitar, Leonard Sheldon, a con artist, pops up and shows him a picture of his child from a previous marriage. He then tries to sell Peter the city of San Diego. Peter refuses to buy it but subsequently swaps his $108 guitar for Blackbeard's treasure map. Then Sheldon tries to sell the guitar to a reluctant Michael who's happens to be passing by. On the Columbia Pictures lot, Micky, Michael and David chide Peter for doing such a dumb thing, but Michael decides they should all set out to find the treasure anyway. David, all dressed up as a ship commodore on a rowboat, starts shouting orders in a military fashion as the guys tries to warn him that the boat is overloaded with too much supplies but David won't hear of it ("Nonsense! Balderdash! We have to be prepared!") and shouts an order to "Launch the ship!" Micky, Michael and Peter do so, and, as expected, the boat sinks, weighed down by its heavy contents-and its occupant, "Commodore" David. After rowing to an Island, the guys begin their search and are soon spooked a sound of a creature's scream.
Meanwhile in a nearby hut, Major Pshaw, who himself has been searching for the treasure for a decade is napping while his native servant Thursday is amused by watching The Monkees TV show, and wonders, "Who writes that stuff?!" As The Monkees continue their search, Michael, in the underbrush, unknowingly walks into some string which sets off an alarm waking Major Pshaw who begins shouting that intruders are attacking his island and soon grabs his rifle that accidentally goes off. Startled by the gunshot, the guys are still convinced that the island is deserted while a wild looking old man watches in the bushes. Major Pshaw tells his man Thursday (a magnificent man Friday, who was hired on a Tuesday and made every day a Sunday) that a fate worse than death awaits Peter, Micky, Michael and David, while The Monkees start to complain of insect problems, prompting Micky to uses a bug spray which, to their dismay, only attracts insects instead of repelling them. Then they are immediately captured in a net hoisted by a crane driven by Thursday!
Major Pshaw invites them for tea and crumpetts, as he grills them. Then he declares to the boys that they won't leave the island alive, since his practice is to shoot all tresspassers. David asks for a fair chance and Thursday persuades his master to give The Monkees a head start. So The Major turns around and begins to count as if playing hide and seek as they flee the hut. Then the Major asks Thursday where they went and since the servant doesn't want to cheat by telling, he simply points. At the beach, The Monkees find their boat missing, hampering any chance they have of escaping! Peter starts wailing blaming himself as Michael consoles him. Then they're frightened off by another sound of a gunshot as the wild looking old man continues to watch on hidden. While strolling through the jungle, they encounter the German Dr. Schwartzkopf, who offers to treat them for malaria, jungle fever and any other illness but the guys just walk away from him. Major Pshaw and Thursday are hot on their trail thanks to a tip from a dirty snake in the grass. Michael decides the guys should all split up to make it harder for the Major to get them all but they hear a Tarzanesque jungle yell and a leopardskin-clad octogenarian swings into view and falls down. The guys can't understand him since he doesn't appear to speak English but only Peter translates from the man's strange lingo ("Kretch!") that he is the original Kimba Of The Jungle, but was abandoned by his movie company in 1916, while his Jane ran off with the casting director who promised her a new career.
As they hear gunshots and the sound of dogs (which is only a loud playback on a tape recorder Thursday's carrying), promises to help The Monkees but gets stuck in quicksand. After they get him unstuck, he calls his jungle friends, in hopes that they will help, but The Monkees are left holding a cat, a puppy, a chicken, and a rabbit. Then Kimba to swing on a vine only to fall into the ground since his swinging days are over. They all later encounter Thursday who claims that's he's defected and offers to show them where the Major has hidden their boat, and they can escape as soon as Pshaw goes to sleep. The guys decide to trust him (since he has a weapon). Thursday takes them all back to the Major's hut too hide since he figures it would be last place the Major would look but lo and behold, The Major shows up capturing them all at gunpoint, figuring that they would think he wouldn't look for them there so he did. David tells him he can't kill them in cold blood since it isn't British as he waves a British flag and although The Major agrees it doesn't count since he's Australian.
He decides to torture them all by bathing them in boiling oil, put bamboo under their fingernails, expose them the ants (with Michael literally being exposed to his three aunts), a tongue lashing (Micky literally getting a lashing by a huge foam tongue) or just simply kill them outright and continue his search for the treasure. Upon hearing this, Peter gives him the treasure map which reveals that the buried treasure has been underneath the hut the whole time and at gunpoint he orders everyone to dig. They dig up a chest and the Major rejoices at the thought of all those gold dubloons as he shoots the lock off with his rifle and opens it. However, instead of gold an elderly lady also draped in Tarzan gear pops out instead and knocks him out with a umbrella. Kimba recognizes her as his long lost love Jane and soon the two old lovers start embracing promising to make pictures together again as David and Peter start crying at the happy reunion. During a romp set to "Daydream Believer", the group is joined by a gorilla, the 3 aunts, and 2 press photographers (both of whom pop out of the chest) as they frantically caper about all over the island. Returned to civilization, Peter is confronted once again by Leonard, who this time tries to sell him the city of Liverpool. Peter accuses him of being a crook who sold him a worthless treasure map tells a police officer as the con artist takes off. But soon the cop offers him the city of Cleveland, sending Peter storming off pouting. The Monkees finish by singing "What Am I Doin' Hangin' 'Round?."