Vanessa and Doof travel to Drusselstein while the boys dig for Mom’s lost wedding ring.
Plot[]
Phineas and the gang are initially planning to build a Bread Bowl Hot Tub, but their plans are derailed when their mom, Linda, accidentally drops her wedding ring down the kitchen sink drain. After their dad, Lawrence, attempts to retrieve it, the ring is washed away into the vast and complex plumbing system. Using a tracking chip Ferb installed, the gang discovers the ring has traveled deep underground, and they decide to build a giant drilling vehicle to retrieve it.
Meanwhile, Doofenshmirtz receives a note from Drusselsteinian authorities, informing his daughter, Vanessa, that she is now eligible for citizenship upon her upcoming 17th birthday. Doofenshmirtz, nostalgic for his old-fashioned and "tragic" hometown, convinces Vanessa to take the trip, hoping she'll connect with her "roots" and develop her own tragic backstory. Doof also informs Vanessa that he never got his own citizenship due to his lack of kicking skills and the fact that his parents weren't there for him. Upon arriving, however, they discover that Gimmelshtump has been completely gentrified, much to Doof's dismay.
As the gang drill underground, they accidentally cut through Agent P's transport tube, sending him directly to his lair. There, he's informed by Major Monogram that his mission is to travel to Gimmelshtump and keep an eye on Doofenshmirtz. Back in the backyard, Candace is excited for a day off from busting her brothers, but the drilling causes her room to shake. She runs outside, trips, and falls down the hole created by the drilling vehicle, landing in Agent P's lair. Carl panics and ejects her from a chair, dropping her into an unknown underground cavern. Candace discovers she's in a cavern filled with mole people, who immediately hail her as their savior. She's rescued by Phineas and Ferb, who have just bored through to a cavern behind the wedding ring. Candace finds the ring but accidentally causes the cavern to collapse, trapping them all.
Simultaneously, Doofenshmirtz is frustrated that Drusselstein has lost all of its "tragic" culture. He creates a Downgrade-inator to restore the town to its former misery. He's confronted by Perry, but during their fight, Doofenshmirtz notices Vanessa is about to take the final citizenship test—a kickball challenge with her parent. Doof reflects on how his parents were never there for him, and decides to give up on his evil plan for Vanessa's sake. Doofenshmirtz helps Vanessa perform the challenge by performing a proper kick on the kickball, thus validating both his and Vanessa's citizenships. During the process, Vanessa accidentally caused Doof to fire his Downgrade-inator at the town's water tower, which sends all the water down a massive crevice. Despite this, Doof and Vanessa are happy of getting both of their citizenships validated, even with Doof agreeing that change can be good in Drusselstein. Seeing that all is well, Perry decides to let Doof spend the rest of his day with Vanessa while flying back to Danville.
The water travels down the crevice and bursts through the rocks, freeing the gang, who drive their vehicle out of the hole, returning to the backyard just as Linda walks outside. The hole is mysteriously sealed, and Perry returns to the backyard just in time. The boys give Linda her ring, and Candace's attempts to tell her mom what happened are dismissed as Linda finds a familiar "ring" to Candace's exasperation.
Cloris Leachman, who voiced Mrs. Doofenshmirtz, Heinz' mom, passed away in 2021 before the series was revived. As a result, she does not physically appear in the episode and was mentioned along with Heinz' father by a note as taking a vacation.
