As he and his companions fly over the Wakka-Wakka River, Scrooge grows impatient, yelling at everyone and scratching himself like he has fleas. According to Mrs. Beakley, Scrooge has caught gold fever, a disease that causes its recipients to itch for gold so much they forget everything else. He orders Launchpad to speed up landing the plane, but when he does that, they find themselves being carried away with the current. Luckily, they avoid going over the waterfall on account of Launchpad opening the loading-bay doors. Scrooge, the trio, Webby, and Mrs. Beakley take a raft outwards, with Launchpad assigned to stay behind and get the plane floating again. Before long, they run into an angry squadron of alligators, whom they manage to evade by puncturing the raft with a knife, thus propelling them away from the gators. They continue onward to the treasure, because there's a pathway leading there. Unbeknownst to any of them, though, El Capitan is not far behind.
Meanwhile, Launchpad has to anchor the plane to the shore, shut the doors, and pump the water out. As he's trying to do that, he is attacked by a snake who tries to drag him underwater. He eventually manages to complete pumping the plane out. After the nephews save Scrooge from a trap planted for anyone dumb enough to follow the suspicion-arousing pathway, Scrooge comes up to an escalator. By now, Scrooge's twitching is worse. Just when it looks like they've reached a dead end, Scrooge and the kids use a tree limb to open the invisible door. Inside is the Valley, where they stumble upon the first fraction of the treasure - a ring of giant golden discs. Just this much is even more gold than in Fort Knox, according to Scrooge, who tries to loosen one of them from the wall, believing he can carry it back to the plane. The disc does loosen, but it ends up falling down the walls, taking the gang with it. Luckily, they jump off at the right time, and the disc hits a hill-disguised temple made of gold. Scrooge, whose gold fever is by now so bad that he's hiccuping and at one point acts like a cat, uncovers the entrance to the temple, where practically every room is made of gold and stocked full of it.
They head inside the central chamber inside the temple and come upon skeletons of deceased explorers who'd also been infected by gold fever. Scrooge refuses to believe he will meet a similar end, and he does not believe the nearby well leads anywhere. Instead, he and the nephews (who are starting to catch gold fever themselves) explore the courtyard, seeing what this place has to offer. As the males check out the chambers of gold dust and gold coins (which, as noted by the nephews, looks identical to Scrooge's Money Bin), Webby tries to translate a "stone" tablet that says that that anyone greedy enough to open all the doors will set off another trap. Scrooge discovers this too late, unknowingly setting off the curse. He is knocked out by one of the gold bricks from the third room, and all the doors shut, trapping the ducks. To make matters worse, El Capitan then arrives, pointing a shotgun at them. El Capitan makes them get into the pot hanging over the aforementioned well, claiming that he has been waiting 400 years for this, and begins to lower them into the so-called lava pit.
Scrooge regains consciousness and begins shivering in spite of the intense heat, which is the final step in gold fever, because the lava is also made of gold. Scrooge declares this to be "the real Treasure of the Golden Suns", and upon hearing this, El Capitan brings them back up, saying he "won't have them tasting a single drop of [his] gold." Scrooge and El Capitan begin fighting, failing to notice the curse's effects. They temporarily stop in order to dodge the floor when they notice it is collapsing and jump to safety. Then the walls start moving, trying dump them all into the golden lava below. It is at this point that Scrooge finally snaps out of his gold fever and uses the vines growing on the walls to climb out with the rest of his group. They even take El Capitan with them, despite his urging to be left with "all the pretty gold". The curse next has the giant gold discs reflecting their light into the lava, causing a volcanic eruption. Launchpad notices this and, believing this to be a rescue flare that Scrooge would signal him for, gets the plane back up and running, and saves everyone. Upon getting out of the destructing Valley, the heroes land back in the river, and El Capitan breaks loose. But when he comes to the spot where the Valley would be, it's now buried under a mountain of dirt. While Scrooge finds this hilarious, the frustrated yet undaunted El Capitan starts trying to dig up the gold. Scrooge heads back to the plane, saying that he wishes he had gotten at least one souvenir out of this. And it turns out he did - another one of the gold lava's eruptions gave the cargo plane a new paint job! Scrooge looks forward to relaxing, saying he's through with treasure hunting, or so he thinks.