Scrooge teams up with his conniving ex-partner and old flame, Goldie O'Gilt, to find a long-lost golden lagoon, but Glomgold has other plans.
During night time, Scrooge and the triplets attend a Gala opening within the Glomgold Wing of the Natural History Museum. When the boys question Scrooge as to why they're attending an event filled with Glomgold's artifacts as a reminder of the times he failed to outwit Scrooge, Scrooge claims it is their responsibility as upstanding citizens of Duckburg to support cultural institutions, but he also wants to secretly take some of Glomgold's food from the buffet to avoid paying for any later. During which time, Scrooge is then shocked to notice his former partner and ex-girlfriend Goldie O'Gilt is also attending the party.
Scrooge and Goldie then greet one another while also mocking their life's achievements, as Glomgold himself approaches them and states to Scrooge that Goldie is his date for the evening (even though Goldie claims she isn't). Nevertheless, before Glomgold can begin to mock Scrooge any further, the ballroom music begins and Goldie and Scrooge take one another's hand for a dance. During the dance, both of them attempt to show off their dancing skills in front of the other, forcing Glomgold to step in with Dewey in an attempt to make Scrooge jealous of his dancing.
As the dance proceeds, both of them explain their reasons for having lived so long, with Goldie claiming to have found the fountain of youth in Rongui and Scrooge claiming to have been stuck in a timeless demon dimension known as Demogorgana. While there he spent his time stopping an uprising that Goldie caused, and during which time Goldie stole the Eye of the Demogorgon, a mystical artifact that keeps the wielder impervious to burns. In order to break up the dance, Glomgold announces to everyone and unveils a skeleton statue for the glacier monster of the Klondike, but suddenly Goldie presses a hidden switch device which then causes a blackout. When the lights come back on, the headpiece to the monster skeleton has disappeared and Goldie is nowhere to be found.
Once they get back in the car, Scrooge orders Launchpad to drive him and the boys home as fast as possible, while the boys continue to mock Scrooge on his supposed romantic relationship with Goldie. Scrooge then states that long ago during the gold rush at Klondike, he and Goldie partnered together to search for a legendary location known as the Golden Lagoon of White Agony Plains. However, Goldie had attempted to steal Scrooge's map, which then leads to a small scuffle that subsequently tore the map in half. Not too soon after were they approached by a giant mammoth that Goldie had unluckily gotten her half of the map stuck in between the teeth of. In order to escape with their lives, Scrooge and Goldie were forced to jump into a nearby stream where they unknowingly trapped themselves in the ice of a glacier for five years.
Because of this, Scrooge believes the only reason Goldie attended the Gala is that she heard about Glomgold recently digging up the Mammoth's skeleton, which she knew would be the perfect opportunity to take back the other half of the map she lost. As they arrive at McDuck Manor, Scrooge realizes Goldie has already arrived and encounters her in his office, with Goldie adding that she had already tied up Mrs. Beakley and Webby earlier. Goldie then gives Scrooge a proposition to return to Klondike with both halves of their map and finally track down the location of the Golden Lagoon of White Agony Plains, to which Scrooge reluctantly agrees knowing that he wants to find it just as much as Goldie.
In Klondike, Goldie and Scrooge gather their materials for the trip while Glomgold secretly proceeds to follow them from a distance. Later on inside the abandoned White Agony cave mines, Scrooge and Goldie remain on untrustworthy terms, with both of them discovering the traps they laid for one another a century ago. When they carry themselves down the elevator shaft, Glomgold arrives from above and cuts the ropes, causing Scrooge to use his pickaxe to slow them down from falling. They continue to move forward and discover an area of the mines known as the Rainbow Caves, a place they know about because they remember the Golden Lagoon is said to be very close to that cave through their map source.
They then enter a dark area of the cave, but when Goldie asks Scrooge for a match, it leads to Scrooges undoing as Goldie ignites a line of gunpowder she had secretly been placing. This forces Scrooge to follow the line to stop the ignition from causing a major cave-in, only for Scrooge to realize it is another one of Goldie's traps as the gunpowder wakes up a sleeping bear from within the caves. Even so, just when Goldie thinks she has the upper hand, Scrooge appears right in front of her while riding the bear as it's revealed he has experience communicating with bears.
Scrooge then ties Goldie to the bear he names Nanook, and they continue further into the caves. However, because of Scrooge's inability to fully understand where the map is telling him to go, he decides to camp for the night in front of the same glacier he and Goldie were trapped in. Scrooge and Goldie then begin to reminisce about their old adventures and betrayals from one another, leading Goldie to question why their past adventure in Klondike is any different. Scrooge reminds Goldie that they spent almost half a decade trapped down in the caves together, but over time he felt they had created a warm feeling for one another that was no longer anger.
Eventually, large cracks of sunlight pierced through the caves, allowing their glacier to finally melt. Goldie's side of the glacier was able to melt faster than Scrooge's, but even though she escaped sooner, she decided not to help Scrooge break apart on his side and left him for dead. Because of this, Scrooge's feelings were betrayed and it leads him to believe Goldie loved gold more than him, but Goldie believes that's the very reason he loved her. Scrooge then decides to untie Goldie from Nanook, and at the same time hears the sound of rushing liquid through a nearby wall. When Nanook smashes the wall open, they discover the Golden Lagoon of White Agony Plains.
However, their cheers of celebration are cut short when Glomgold arrives and reveals that he and Goldie have been working together the entire time. Scrooge then questions as to how their partnership came to be, to which Goldie explains that yesterday during the Gala, she and Glomgold teamed up together with a plan to con Scrooge out of using his half of the map so he could find the treasure for them. Regardless, Scrooge begins to swordfight with Goldie using one another's pickaxes while Glomgold attempts to intervene using a nearby shovel, but fails.
As the fight proceeds on a bridge above the stream of liquid gold, Glomgold throws his shovel towards a hanging rock formation positioned above Scrooge and Goldie. As the rock falls down on them, Goldie shoves Scrooge out of the way and the bridge then falls apart, causing Goldie to fall into the liquid gold. Suddenly, Scrooge is knocked unconscious from behind, and before he knows it he's now tied to one of Glomgold's watchtowers. Glomgold begins to mock Scrooge from below while stating how he now has the Golden Lagoon of White Agony Plains to himself, as well as a golden statue of Goldie next to him. Glomgold then explains his intentions to use the golden liquid to melt the tower Scrooge is tied to, killing him and thus making Glomgold the richest duck in the world.
However, as Glomgold pulls the lever, he realizes his pipe system has been tampered with, as a tube connecting to a large tank attached to a ship is now streaming the liquid gold away. When Glomgold then realizes Goldie's not inside the gold statue, both Scrooge and Glomgold witness Goldie leaving on the ship with the liquid gold, as it's revealed the Eye of the Demogorgon saved her from burning to a crisp. Even with Glomgold's furious state of his own, Scrooge is unable to feel betrayed but more so impressed at Goldie's entire scheme. Back at McDuck Manor, Scrooge enters the mansion only to be further mocked by the triplets about him and Goldie's most recent adventure.
Scrooge then makes his way back to his office to get his top hat he left on his chair, only to discover a hidden parcel inside the hat. He opens it and discovers a small idol inside, as well as a photo of Goldie standing behind a lost temple. The letter on the photo reads "Next time you need some gold in your life, come find me! XOXO always" much to Scrooge's joy.
Flintheart Glomgold begins paraphrasing Belloq's taunts to Indiana Jones from Raiders of the Lost Ark with "Once again, Scrooge, you see there is nothing you can possess that I cannot-" before realizing that Scrooge McDuck has stolen food from his gala buffet.