Dewey tries to prove himself by exploring a frozen fortress in search of a money tree seed, but Glomgold has kidnapped Scrooge in order to find it first.
Della is seen making numerous flying stunts with the Sunchaser (to which Della refers to as the Cloudslayer), much to her son Dewey's excitement for witnessing his mother's flying skills for the first time, and her uncle Scrooge's regret as he was beginning to get nauseous. Dewey and Della were still in the adventurous spirit, but Scrooge reminds them that they are merely travelling on a business venture in Boarway. He also states that the country is home to a sterile seed depository facility known as the Doomsday Vault, built by his old colleague Ludwig Von Drake. Scrooge explains that Ludwig had collected millions of seeds from around the globe, in the event that if a supposed apocalypse were to ever occur, society could prosper with the seeds he had stored for safe keeping.
However, the vault had recently been damaged by melting permafrost, so Scrooge expresses his intentions to convince the current owners to hire McDuck Bin Securities to fix the ongoing conflict. Soon after Della lands the plane, the three run into Flintheart Glomgold and Zan Owlson, both of whom also have the same intentions as Scrooge for the trip. The group is later seen within the office building close to the vault, as Scrooge presents his envisions for the safety of the vault to Ludwig's children and current owners of the vault Corvus, Anya, and Klara Von Drake. He goes on to explain about the many resourceful materials he promises to remain guarded until the end of the world, including a mythical seed known as the Fabled Money Tree of Oramorus, catching Flintheart's attention.
This, however, encourages both Della and Dewey to enter the vault itself, and get a head start to take a good look at the money tree seeds before Scrooge locks them up for good. Meanwhile, Glomgold begins his own presentation on why he is the most suitable choice to hire for securing the vault, but he blows it after admitting his intentions to break into the vault, steal the money tree seeds, split the profits and destroy the vault to cover his tracks. This leads Glomgold and Owlson to lose the contract to Scrooge, Leaving Owlson infuriated at Glomgold and his non-stop brainless plots. As Scrooge bids farewell to his competitors, he soon after realizes that Della and Dewey had taken the Sunchaser after noticing their disappearance.
Meanwhile Dewey and Della were flying towards the vault while singing Stand Out during the flight. Believing that Dewey has proven to be the adventure material, Della encourages him to fly the Sunchaser, but it ultimately leads them to crashing close to the entrance of the Doomsday Vault. Meanwhile, Scrooge phones Mrs. Beakley to update her on the current predicament, but to his surprise is cuffed behind his back by Glomgold, and the two were now stuck together. Having placed a tracker on the Sunchaser and knowing it is close to the vault, Scrooge has no choice but to escort himself and Glomgold towards the vault in the hopes of making his way towards the plane to return to Duckburg, and keeping Dewey and Della out of trouble, but they both have to walk to the plane as Glomgold tells Scrooge that Owlson took the former's plane.
Scrooge tries to convince Glomgold that they needed to make their way back to base camp to prepare for the long walking distance to the vault, but Glomgold's impatience eventually leads to a scuffle between the two on thin ice, and soon after both of them falling through the cracks into the freezing water. Meanwhile, Dewey and Della were still making their way through the cave until they finally came across the entrance to the Doomsday Vault just outside of it. But as they enter, Della accidentally steps on a security beam as the entrance door then slides closed, trapping them inside.
Suddenly, Professor Ludwig Von Drake appears via recordings congratulating the "survivors" about surviving the apocalypse. Della notes that climate change has made the vault defective and thus almost fails to operate. Von Drake sings the passcode to gain access to the vault, but the colored buttons are frozen, so Dewey has to crawl through an air duct to get his mother further inside. Dewey pulls on the panel causing the ceiling on Della's end to descend slowly. As Ludwig is advising Dewey on how to bypass the descending ceiling anti-intruder trap, Della struggles to hold the ceiling back. Just then, sweat drops from the blue-clothed duck's face and shorts out the wires, saving Della from being crushed.
As the mother-son duo venture further in, Scrooge and Glomgold arrive moments later freezing from going on foot. Scrooge spots the damaged wires for the ceiling trap which will cost him millions to repair. Glomgold decides to warm himself with a fire which will only worsen the damaged condition of the vault. When Scrooge insists on pressing forward, Glomgold lights some gasoline setting the room they are in on fire.
Della and Dewey ride an elevator into the seed vault, the main structure of the Doomsday Vault. Ludwig's recordings brief the amount of seeds needed to help the Earth survive a cataclysm. The seeds are treated with Von Drake Supergrowth Formula so the survivors won't starve. Because the formula will grow the plants at fast rates, they are not to be planted within miles of one another for safety. The pair reach the controls and find a drawer containing the Money Tree seeds, but the crane malfunctions before it can be put to use.
When Della decides to call it quits, she finds Dewey climbing the drawers. Just then, the broken crane spills some of the Supergrowth Formula. Della tells Dewey to climb the draws like rock climbing then after getting a glance at the seeds, they would head back. Della then worries for her son because of the heights they are in. Dewey nearly suffers claustrophobia and falls, but saves himself and climbs back up to the designated drawer. Dewey opens the drawer and glances at the Money Tree seeds, but just as it seems like mission accomplished, the drawer bends and the seeds fall to the spilt growing formula.
On their part, Scrooge struggles to smother the fires Glomgold had lit, then another Ludwig recording says he would activate the emergency sprinklers and seal the room to preserve the seeds. Glomgold tries to break for it, but gets his leg caught in the shutters. With the panel broken and the air ducts also broken, Scrooge scolds Della's actions to himself and lifts the shutter by hand. Scrooge takes a pipe and part of Glomgold's winter jacket and uses the fire to melt the ice blocking the sprinklers, thus putting out the fire.
With the Money Tree growing and sprouting money, Dewey holds on for dear life when Scrooge and Glomgold still shackled arrive. Glomgold worries his rival is trying to "counter-scheme" him by sending Della and Dewey to get the seeds. Della tries to encourage Dewey to get momentum, but he falls; Thankfully, his mother saves him and they stand on the broken crane. While Glomgold tries to procure some dollar bills, some debris slings the crane arm holding Della and Dewey to Scrooge's side unshackling him from their rival.
Scrooge then scolds Della for going ahead in the plane, jeopardizing the rich uncle duck and wrecking the very hope the world needs to survive the apocalypse. Seeing some of the tree providing enough route to slide safely down, Della using the idea jumps with Scrooge and Dewey to the tree and slide their way down while Glomgold falls. At the bottom, having memorized the structural plans for the vault and how she pays attention to exit strategies, Della and company exit through the emergency exit.
Outside, Dewey cries over his failure to prove himself, but Della assures her blue-shirted son she can always believe he can do whatever he puts his mind to. Just as Glomgold confidently says that the McDuck-Von Drake contract is terminated, Della seeing the grown money tree has an idea on how to rectify the mess she caused. Moments later, the gold from the tree is used to repair the vault as Della remembered to how she welded gold on the Moon, saving Scrooge millions in construction. Dewey then returns some of the Money Tree seeds for Della to return to the vault. While Glomgold spies on the repaired vault with his drone, the money he tried to steal earlier is blown away by a breeze, and Glomgold and the drone fall through thin ice once again costing him a chance to win the wager and usurp McDuck's company.
A Powerline CD case is also visible on the Sun Chaser's dashboard as Della and Dewey sing.
The Sunchaser’s original name was the “Cloud Slayer”, before Della’s disappearance. Launchpad presumably renamed it to the “Sunchaser” after her disappearance.
Dewey reveals that his middle name is Dingus, making his full name Dewford Dingus Duck.
In the scene where Glomgold gets kicked out of the building, you can see the rebel shield generators as seen on Hoth form the Star Wars franchise.
The moment where Della is nearly crushed by the falling ceiling trap pays homage to the ceiling death trap from Indiana Jones and the Temple of Doom.
The Doomsday Vault in Boarway is inspired by the real-life Svalbard Global Seed Vault in Svalbard, an Arctic Ocean archipelago belonging to Norway. It also contains seeds meant to be safely kept for future human survival. Unlike the fictional Doomsday Vault, the SGSV was designed to survive climate change, but it still notably suffered damage in October 2016 when warm weather and heavy rainfall caused water to enter the facility; the seeds themselves were not damaged, however.
The order in which the code to the colored-button keypad is a reference to the The Spectrum Song, which Ludwig sang.