Over the next few days, Inspector Harriet Marblemaw continues her inspection with relentless criticism, arriving one morning to find the children cheering Theodore’s egg-eating record attempt and enduring their jokes as well as Calliope’s deliberate hairball. Arthur tries to keep the household calm while steering Marblemaw toward reviewing lesson plans, but Marblemaw fixates on “manners,” government-approved books, and whether the island encourages anti-government sentiment through trips to the village.

In Arthur’s office, Marblemaw challenges Arthur’s authority, questions the adoption process, and needles him about DICOMY protocol. Arthur pushes back against outdated, demeaning curriculum and announces that Linus has proposed and Arthur has accepted, briefly surprising Marblemaw into offering congratulations. Marblemaw then targets David, insisting he is not an adult and demanding proof of Arthur’s claim about his age; a magically delivered note tells Arthur to open his top drawer, where he finds old photographs of himself at different ages with David beside him. The proof unsettles Marblemaw, who abruptly leaves and schedules individual interviews with each child.

Marblemaw interviews the children one by one, and the meetings quietly backfire on her: Talia triggers Marblemaw’s pollen allergies, Theodore leaves with one of Marblemaw’s coat buttons, and Phee reports Marblemaw’s obsession with “thieving dragons.” Lucy’s short meeting ends with Lucy seemingly unbothered, while Sal’s longer talk leaves Marblemaw oddly pleased. Arthur suspects the photographs were arranged by magical help, and he warns Marblemaw that Lucy’s coming Saturday adventure will be memorable.

On Saturday, the group heads into the village, and Lucy surprises everyone by planning separate, thoughtful outings for each sibling while keeping David with Arthur—ensuring Marblemaw follows and cannot be cruel to him. Arthur, Lucy, David, and Marblemaw go to J-Bone’s record shop, where David relaxes as Lucy and J-Bone share music, and Arthur joins in their dancing and scatting. Lucy explains to Arthur that making his family happy quiets the “spiders” in his head, and that protecting David is part of Lucy’s plan, even as Lucy still revels in “monster things” as jokes and threats.

The calm breaks when J-Bone runs from the shop with David playfully chasing; Marblemaw seizes David in the street, twisting his wrist and calling him an animal. Arthur’s phoenix begins to flare, but Lucy warns Arthur that Marblemaw wants that reaction. The other children arrive immediately—because Lucy “called” to them in their heads—and the family closes ranks as Phee threatens Marblemaw with turning her into a tree if she touches them again. Linus points out there are witnesses, and the onlookers ultimately cheer for David, undercutting Marblemaw’s narrative. Marblemaw is ferried back by Merle, while David returns with a bruised wrist and Arthur vows Marblemaw has made an enemy.

That night Arthur cannot sleep and discovers Phee in the gazebo magically forming saplings, still angry and determined to protect the family. Arthur counsels her about consequences while affirming her goodness, and Phee urges Arthur to ask David to stay permanently once Marblemaw is gone. Phee then admits what she wants: to fly with Arthur as the phoenix. Arthur transforms, and he and Phee race around the island through the night, ending at the sandbar where Phee sleeps against him as dawn rises, urging Arthur not to hide this part of himself.