Webby is searching for the boys in McDuck Manor, but becomes distracted by Penumbra who is living in their backyard attempting to fix her ship so that she can return to the moon. Webby extends an invitation to hang out with her, but she turns her down, wanting to return home as soon as possible. She eventually finds Dewey and Louie watching Ottoman Empire when a commercial for Flintheart Glomgold's latest venture comes on; the "Flint Ferris Glom Wheel". Webby reluctantly decides to go while Dewey also wants to come due to an incident involving another child named Timmy Jenkins getting media attention from Glomgold's previous failed ride.
Della visits Penumbra who is hard at work on her ship, and she determines that she is afraid of trying new things. Penumbra reveals that she did have coffee with Launchpad, but that did not go over well. Webby and Dewey arrive asking for Penumbra to join them at the pier where she once again turns them down so that she can discuss her departure with the rest of her people. However, while discussing this with Gibbous and Zenith, she learns that all the other aliens do not want to return home. They further admit that none of them think that Penumbra is capable of having fun. Spurned by this, Penumbra accepts Webby's invitation.
Gibbous is revealed to have been hired by Glomgold to be his assistant as he is unaware of his treachery, or the fact that he constantly mentions them as the threat that he defeated. Glomgold's new Ferris wheel is part of a grander scheme and wants nothing to go wrong. Launchpad drives Penumbra, Dewey and Webby to the pier, but is nervous trying to talk to Penumbra as he knows that the date went bad and wants to make it up to her. During the transit, Launchpad falls out the limo and Penumbra tries to stop it, only for Webby to do so by stomping on the brakes, while Penumbra lands on a pile of fish.
Webby and Dewey show Penumbra around on the pier and attempt to get her to enjoy herself. However, Penumbra fails to enjoy any of the activities. While all this is going on, Launchpad tries to speak to her, but constantly chickens out. Glomgold's ferris wheel turns out to not be up to code, while discussing it with Gibbous, he sarcastically asks him to call the safety inspector, which he does. Eventually, Penumbra breaks down and declares that earth is the worst and that she has no place being there. Webby admits that she was afraid when she first left McDuck Manor, but that she made a new version of herself and that she can too if she gives it a chance. She offers her a burger and Penumbra ends up liking it; gorging several down.
In the evening, Webby offers Penumbra an ice cream sundae and she eats it hurriedly, causing her to get brain freeze. The safety inspector arrives and immediately declares the ferris wheel unsafe. Upon seeing Penumbra acting wild over the brain freeze, Glomgold shifts the blame to her and everyone begins to chase her, causing her to hate earth again. They run to the Ferris wheel, but Webby and Dewey end up getting stuck in one of the cars and end up at the top. Glomgold reveals that his Ferris wheel is actually a cannon, set to be aimed at McDuck Manor, though the safety inspector states that it is unlikely to be effective and will collapse on itself.
With Launchpad and Gibbous' help, Penumbra manages to get to the top of the ferris wheel, declaring that she is having fun now, and rescues the children before the wheel collapses. Glomgold attempts to fire the cannonball from the wheel, but it lands on his foot instead, and collapses from the weight of the papers from the safety inspector which are the fines for both safety violations and damages to the Pier, along with a letter from Jenkins. Launchpad finally talks to Penumbra who tells him that while she is not interested in dating him, she does consider him a formidable ally and would not mind fighting alongside him. Dewey once again fails to get media recognition with Jenkins getting the spotlight despite not getting on the ride.
Penumbra, now wearing a t-shirt and lacking her helmet, recounts the story to Gibbous, Zenith and Della with Webby and Dewey beside her. She adds that she will stay on earth as long as she wants, or at least as long as it needs saving. Launchpad arrives to pick them up, with Penumbra learning that he is "surprisingly adapt at dismantling aircraft", as she decided to take apart her ship. She happily brings Della and the kids along as they head back to McDuck Manor.