Ben, Gwen, and Max go on a tour of the impervious Fort Knox, but when Dr. Animo sticks a hungry ani-mutate on the Fort, Ben must stop it before it gobbles up the nation's monitory standard!
Ben, Gwen, and Max are on a tour of the Laughlin Mint & Museum, with the former two expressing their boredom of the entire trip. Max, however, continues to show great interest and excitement for the tour. Meanwhile, outside the museum, Dr. Animo leads Slurpstack into the museum - as an attempt of collecting all the museum's gold of which the latter will eat for him. However, before the plan can be carried out, Slurpstack eats his transmitter before proceeding to make his way into the museum, whilst eating everything blocking his path.
Back inside the museum, after another unsuccessful attempt to be amused, Ben heads to a vending machine when Slurpstack suddenly breaks in and begins eating all the stacks of gold. Despite this, however, eating more and more gold shows visible pain for Slurpstack, yet the mutant still continues to eat everything in sight and grows even more enraged and aggressive. Seeing this, Gwen tries to help the mutant, but is put at further risk of endangerment - thus prompting Ben to turn into Stinkfly. He then proceeds to fly around Slurpstack and mock the latter for failing to catch him. However, this only annoys Slurpstack to the point of eating Max, much to the horror and shock of both Stinkfly and Gwen, before he lies down.
Stinkfly then times out, with Ben commenting that he will have to think more decisively in order to rescue Max from within Slurpstack. He ultimately decides to turn into Grey Matter, where he then concludes that going inside Slurpstack itself would be the best decision to save Max. With this, he ventures inside the mutant, although the trip is shown to take evidently longer than he expected it to be.
Meanwhile, inside the mutant's stomach, Max wakes up disgusted at the monster's insides. Grey Matter, on the other hand, continues his navigation inside Slurpstack, using his immense knowledge of the mutant's anatomy to successfully steer his way around to the stomach. Outside, Gwen tries to save the crowd of confused tourists, but she herself becomes trapped in the same room as the mutant. As Grey Matter reaches Max, the two of them are interrupted as Slurpstack begins to once more rampage around at his pain. This subsequently prompts Gwen to lure Slurpstack by luring him with the 'candy' that he wants. Her plan succeeds, and the mutant stops rampaging under her influence - thus buying Grey Matter enough time to enact his plan, involving the building of a rocket constructed of gold bars around Max, to ride them out upon his forcing of Slurpstack's reflexes whilst Animo observes and acknowledges the alien's intellect at work. Grey Matter's plan works, forcing Slurpstack to vomit all the gold bars out as well as him and Max (as well as Animo's transmitter). With Max now safe outside the mutant's reach, he proceeds to take down Slurpstack by once more prompting certain nerves, using his biological knowledge of the mutant.
However, as Slurpstack lies defeated, Max reminds Ben that he is still stuck inside the rocket of gold bars, to which Ben comments (after timing out as Grey Matter) that he has no clue how to free him from it. Animo, however, claims it to be 'rightfully' his, communicating through his bird transmitter, and thus announcing his presence to the trio. Gwen, angry at the sight of Animo, crushes his transmitter - thus ending the episode.