Carl studies the sand ooze climbing the stairs and realizes it slows as it stretches thin. Ghazi has already explained that the only way to stop the borough boss, Mrs. Ghazi, is to burn its core beneath a recliner in the basement. Because normal fire is not enough and explosives might collapse the glass structure, Carl settles on a risky plan: Donut will open a Hole from the floor above, and Carl will use his Sticky Feet ability to cross the basement ceiling upside down and pour burn gel directly onto the chair above the core.

While Katia stays near the stairs with Ghazi, Carl and Donut set up in the fountain room. Katia throws one of Carl’s music traps down the stairwell, blasting “Jump Around” to distract the ooze. Donut opens the Hole, revealing the ruined boss chamber and the glowing core under the recliner. Carl lowers himself in by rope, activates Sticky Feet, and carefully shuffles across the ceiling while Katia throws more distractions and clockwork mongos into danger to keep the ooze occupied.

At the recliner, Carl chooses not to move the chair because that would likely alert the ooze sooner. Instead, Carl coats it with burn gel and ignites it. The flames erupt hotter than expected, exposing the core and finally triggering the boss health bar as the ooze retracts and takes heavy damage. Just as victory seems certain, the chamber collapses. Sand buries Carl and Donut, but Donut grabs Carl’s foot and drags him into a small surviving pocket. They realize they are trapped under multiple stories of unstable sand and cracking debris, with almost no oxygen left.

Carl tells Katia to escape with Ghazi, partly to save her and partly because Carl still hopes Ghazi might be needed to explain the winding box. Outside, Katia reports that Ghazi is panicking over his crystallized doll. Gwen warns that the storm door is flickering and urges them to get out. When Carl’s instructions fail to restore the castle, Katia ends up killing Ghazi during a brief fight and loots a note explaining the winding box, but his death changes nothing. With the ceiling continuing to split, Carl abandons any rescue plan and orders Donut to use water-breathing scrolls and Mordecai’s special brew if needed.

Gwen has Tran partially open the water valve, and the incoming flood smashes through the collapsing structure. Carl wraps himself around Donut as they are violently swept out of the sandcastle and into the water quadrant. Both are badly injured by the debris, and Donut is knocked unconscious after being pierced by glass, but Carl repeatedly heals her and keeps them moving upward underwater. Once Carl confirms to Katia and Mordecai that they are alive, Gwen sarcastically notes that this disaster might have been avoided if Carl had let her flood the place sooner. As Carl and the recovering Donut rise through the dark water, a large predator begins feeding on the bodies falling around them, and Donut wakes in full panic.