The children gather on the porch after Arthur’s phoenix outburst, and Harriet Marblemaw storms up accusing Arthur of breaking a window and endangering others. When she produces only a snail shell as “proof,” Zoe cuts her off and, using powerful magic, forcibly slides Marblemaw back into the guesthouse and shuts her in. Lucy then reinforces the home by turning all windows into thick plastic.

Arthur cancels classes to address the real crisis: Marblemaw is at the orphanage under false pretenses and is not there for the children’s welfare. Sal refuses to be shielded and insists the children deserve the truth, arguing they already live in the “crosshairs.” Sal also names the additional burdens Arthur and Linus cannot fully understand for him, especially navigating being Black as well as human and magical, and demands trust and partnership.

Sal calls Arthur “Dad” and Linus “Papa,” and the other children confirm it as their decision, overwhelming both adults with emotion. Arthur admits he has been overprotective and agrees to include them. He reveals Marblemaw is working for Jeanine Rowder and intends to take the children away to increase Rowder’s power, but Arthur, Linus, and Zoe vow to stop it.

The family then openly invites David to make the island his home too, without replacing his birth parents or forcing him to call Arthur “Dad.” David asks to keep contact with Jason and B and to have space for his plays; Arthur and Linus agree, and David commits to staying. The children pile onto David in celebration, while Linus declares they will protect their home and fight back.

Later, in the sitting room, Sal proposes they not banish Marblemaw yet, to avoid alerting DICOMY before they are ready. Zoe hints she has a serious, irreversible plan forming. Inspired by David’s desire to scare rather than harm, Sal suggests they “weaponize” fear against Marblemaw by frightening her as the “monsters” the government claims they are—while Lucy insists they should not kill her, both for strategy and because he wants to be nice. Everyone agrees to put Marblemaw in her place without maiming, and Arthur asks Sal to explain the plan in full.