The Kangs fire crossbows at the cleaner and free the Doctor. They flee back upstairs.
The tube ascends and the Chief staggers out, now taken over by Kroagnon. In slurred tones, he addresses the cleaners and tells them that he is finally free. They will now destroy the remaining inhabitants.
The Kangs, at the Doctor's urging, gather all their surviving members and ascend to the pool.
Mel takes a swim and the robot crab attacks her. She screams for help but Pex is too scared to do anything. She finally gets to the edge of the pool, takes his gun and destroys the crab.
The Deputy activates an emergency protocol to gather all the surviving caretakers. The Doctor and the Kangs reach the pool and reunite with Mel and Pex. Kroagnon and the cleaners ascend the towers, wiping out everyone they encounter.
The Kangs begin to taunt Pex again. He is about to leave when the surviving Residents arrive.
Kroagnon arrives at the Caretaker headquarters and begins to rave about the towers being polluted with living flesh. The Deputy quickly realizes that the Chief isn't himself and runs.
Maddy tells the Doctor about Kroagnon and the cleaners. She apologizes for the Rezzies' behaviour and gets the Kangs to agree to work together. The Caretakers arrive next.
The Doctor decides they need to trap Kroagnon and destroy the cleaning machines. The Deputy knows where explosives can be obtained and the Kangs and Rezzies hatch a plan to stop the cleaners. The Doctor realizes that the only way to draw Kroagnon out is to trick him into a meeting. Pex offers to lead Kroagnon into the trap.
As the Rezzies and Kangs take out several cleaning machines, the Doctor contacts Kroagnon and criticizes his design, driving the Great Architect into a rage. Pex contacts Kroagnon and offers to lead him to the Doctor. As he meets with Kroagnon, the Doctor and the Kangs rig the hideout with explosives.
Pex becomes nervous and leads Kroagnon to the hideout before the trap is set. The Doctor improvises and tries to trick Kroagnon in, but fails. Pex is about to run again, but finds his courage and attacks the Great Architect. They fall together into the hideout, which goes up in flames.
The Kangs hold a funeral for Pex. The residents of the towers, all united, bid farewell to the Doctor and Mel, with Fire Escape giving him a Kang scarf in both blue and red colors. As they take off, graffiti is revealed that reads, "Pex Lives".