Standing at the top of the stairs, suddenly the darkness created by the darkbulbs switches off and turns to twilight, and Iff and Haroun can see into the ship. They follow Khattam-Shud into the ship's belly, and Haroun thinks that the Chupwalas look like rock stars as they don "rather fashionable wrap-around dark glasses" to help them see. Iff and Haroun look around at all the whirring and clanking machinery surrounding them.
The "rather fashionable" dark glasses add a sense of absurdity to the situation, which is already a confusing combination of the appearance of normalcy and true evil. Remember too that twilight represents a balance point between light and dark, where neither the Chupwalas nor the Guppees can see perfectly.
Khattam-Shud begins to explain that each story in the Ocean requires its own type of poison to properly ruin it, and suggests how one can ruin different types of stories. Iff mutters that to ruin an Ocean of Stories, you add a Khattam-Shud. The Cultmaster continues that each story has an anti-story that cancels the original story out, which he mixes on the ship and pours into the ocean. Haroun, stunned, asks why Khattam-Shud hates stories so much, and says that stories are fun. Khattam Shud replies that the world isn't for fun, it's for controlling. He continues that in each story there is a world he cannot control, which is why he must kill them.
Iff here simplifies Khattam-Shud's explanation, as all that's needed to really end a story is to say it's over. However, Khattam-Shud is working to not just end stories by simply saying they're over, but to make them unappealing to audiences, which will then insure that they won't be told, Silence Laws or not. Think about the ancient stories around the Wellspring; they exist as an example of what happens when stories are deemed boring and not useful.
After 11 minutes, Haroun stops listening but continues following Khattam-Shud and Iff. He starts paying attention again when he hears Khattam-Shud mention "the Plug." Khattam-Shud explains to a horrified Iff that the crane on deck is suspending a massive Plug that is being constructed by divers to fit perfectly into the Wellspring, so that no more stories can flow to make Khattam-Shud's work more difficult, and then the Ocean will freeze over.
Khattam-Shud isn't just working to squash the stories already in existence; the Plug will function to stop creativity from even existing. The importance of this statement is indicated by the fact that even after Haroun has reached his 11-minute attention span, a mention of the Plug is dire enough to bring his attention back to the conversation.
Haroun asks how the divers can survive in the water without being hurt, and Khattam-Shud shows him a cabinet of protective suits, and then points out their Generator, which is the ship's sole power supply. Suddenly, through a porthole, vegetal tendrils enter the ship, and Haroun recognizes Mali (Haroun will later learn that Mali escaped capture by pretending to be lifeless roots). Mali leaps at the Generator as Khattam-Shud yells for his minions to switch on the darkness, but Mali pokes roots and vines into the machine, cutting off the ship's power supply. Chupwalas try to attack him, but Mali only sings.
It's an interesting turn that the Chupwalas are affected by the poisons in the same way the Guppees and the stories are. This alludes to the idea that attempting to censor language, ideas, or people is tricky and harmful for the censors as well as the censored. Further, the fact that they're all affected by the poison draws similarities between the Chupwalas and the Guppees, further supporting Haroun's thought that they'd find each other interesting.
Haroun, noticing that Khattam-Shud's attention is not on him, bites the Bite-a-Lite. Light pours from his mouth, scattering shrieking and cursing Chupwalas who are blinded by the light. Haroun grabs Butt's brain-box from Khattam-Shud and runs for the cupboard of diving suits. He tries frantically to put on a suit. As he struggles, he notices that none of the Chupwalas have shadows and are therefore shadows themselves. He notices too that with the glare of the light, the Chupwalas become more shadowy, and he wishes that the sun would come out. As Haroun's two minutes of light run out, he manages to zip his suit, put on goggles, and dive out a window into the Ocean.
Even though Haroun struggles practically during his two minutes of light, he's able to gather extremely important information. By understanding that the Chupwalas aboard the ship are only shadows and are therefore inherently out of balance, Haroun will later be able to make the jump to understanding how to defeat them.
Haroun is overcome with hopelessness as he hits the water, and he falls through the Ocean. He sinks deep enough to see the Plug, which is the size of a football stadium. Still sinking, he finally catches sight of the Source of Stories, a giant chasm in the seabed with pure, colorful, unpolluted Streams of Story flowing up from it. Haroun suddenly understands that if he can stop the Source from being Plugged, he can save the Ocean. One of Haroun's hands brushes against a pocket in his nightshirt and feels something in there. He knows he put Butt's brain-box in another pocket, and then realizes what's in this pocket and knows what he can do.
Haroun's glimpse of the Source of Stories indicates a great reverence for creativity and creative thought. Similarly to how the Story Water is a physical representation of stories, the Wellspring is a physical representation of where the stories come from. This sight is magnificent enough to trigger Haroun's epiphany of how to save the Ocean.
Returning to the surface, Haroun notices that he's come up right next to the disabled Butt the Hoopoe. He sees a search party of Chupwalas looking for him heading towards the weed jungle. Haroun pulls out Butt's brain-box, climbs onto Butt's back, and lifts the lid of Butt's head. He sees three leads and three matching connector points on the brain box. When he plugs them in, Butt begins to sing a strange song, and Haroun quickly disconnects the wires. Plugging them in differently, Butt begins to buck, and Haroun disconnects and reconnects the leads one more time. Haroun then hears Butt's voice in his head, asking what took so long. Haroun asks Butt to stay still and pretend it's still missing its brain.
The three tries to reconnect Butt's brain box is a nod to the rule of three that is so prevalent in fairy tales (essentially the convention that things happen in threes, à la the three little pigs, or the story of Goldilocks). This again situates Haroun's story as being a part of the greater world library and not as a standalone entity, and also provides the reader another avenue through which to make connections to the many outside works that rely on the convention.
Haroun reaches into his other pocket and pulls out the half-full bottle of Wishwater that Iff had given him earlier. Haroun drinks the water, thinking it might take more than 11 minutes, but he'll try. Closing his eyes, Haroun wishes that Kahani would turn and the sun would shine down on the ship. Butt says that Haroun's willpower is now up against the Processes Too Complicated To Explain.
Haroun realizes that shadows are unable to exist in sunlight without a Self to be attached to. In this moment, Haroun is embracing the absurdity and the storybook logic of Kahani in order to accomplish the impossible and overpower extremely complicated, inherently rational science.
Haroun lies on Butt's back, concentrating, for 11 minutes, at which point the Chupwala search team notices him. As they began to charge towards him, Haroun's wish comes true: Kahani turns and the sun rises.
Haroun's wish comes true once he's able to power past the 11-minute mark in this climactic moment. It's simultaneously a breakthrough for Haroun personally as well as an act that destroys the Guppees' censorship.
Haroun opens his eyes to the sunlight. Chupwalas begin to shrink and melt, and the ship is doing the same. Haroun, yelling for Iff and Mali, runs up the gangway. When he reaches the deck, it feels like tar beneath his feet. Poison is evaporating from cauldrons, and Iff and Mali, suspended by ropes woven from shadows over cauldrons, fall into the cauldrons. They are able to tear out holes in the now-empty (and softened) cauldrons and escape. The three of them race down the gangway and onto Butt's back. Butt swims quickly away from the ship and into the weeds, and then a burning smell comes from Butt's head and Butt stops.
Haroun was right in his evaluation that the ship and this Khattam-Shud are shadows, and therefore inherently off balance. Here, the opposite of the environment that these Chupwalas are used to is what destroys them. Consider the fact that now that Kahani will rotate normally, this kind of imbalance attained by detaching from one's shadow will be wholly impossible. By putting Kahani back into balance, Haroun restores balance to the Chupwalas as well.
Iff declares that Butt has blown a fuse and Haroun feels responsible for ruining Butt. Iff says that a mechanical brain can be replaced, and if they can make it to the Service Station in Gup City, they'll be fine. Mali offers to push, and as he begins, they hear a sucking sound as Khattam-Shud's ship melts away and the plug falls to the ocean floor. After pushing for several hours, Mali can push no further. Suddenly, Goopy and Bagha appear out of the Ocean and offer to pull them.
Haroun's deep sense of responsibility for those around him crops up again as Butt blows a fuse. However, we're again reminded of the benefits of being a machine, as Butt's brain is simply replaceable.
Haroun wonders out loud what happened to Khattam-Shud, and Iff shrugs and says that he certainly melted like the other shadows. Haroun thinks of everyone still battling the real Khattam-Shud, and thinks of Blabbermouth. He thinks too that Kahani will now be a sensible moon with day and night.
Keep in mind here that the real Khattam-Shud is now hopelessly out of balance, as his Self-like Shadow is entirely gone. This will put him at a disadvantage as he battles the Guppee Army. Meanwhile Haroun has brought a huge change in favor of balance—making Kahani experience both day and night, not just one or the other.