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To get more information about Bus 23, Lisa and Bart ask Nelson. Nelson explains Bus 23 was a bus full of children that was supposed to drive over a dangerous ice bridge but was never heard from again, as Skinner and Superintendent Chalmers covered up the loss of the children. Lisa tells Bart about the room, and the two ask Homer to fly them to the lake where the ice bridge would be. Lisa falls out of the blimp and into the water, where she sees the submerged Bus 23, and Homer dives in to save her. However, they find that all the "children" inside it are actually mannequins. Homer and Lisa are saved by the Pooter Toot Express, which knocks over a tree for them to grab onto just before it falls apart. The mysterious figure is revealed to be Otto, who is relieved to discover he is not responsible for the death of the children, as he was the driver of Bus 23.
Chalmers and Skinner try to flee to Bolivia, but are stopped by Bart, who has Skinner's car key and forces them to explain everything. Years earlier, the school had received a large grant for the purpose of improving its classrooms. Skinner cashed the check but left the money in his pants pocket, and his mother inadvertently destroyed it when she washed his laundry. With the help of Groundskeeper Willie, Chalmers and Skinner built a fake classroom and photographed it to fool the government, using rented mannequins to pose as students. They put the mannequins on Bus 23 to have Otto return them before having to be charged for the extra day, but the ice bridge gave out and the bus went into the lake. Chalmers and Skinner apologize to Otto for letting him believe he killed a busload of students, and all is forgiven. No further mention of the rental money is made, though Skinner says that they anticipated the wedding cakes but not Maggie locking herself in the car, and Chalmers chastises him for not anticipating her birth.
The epilogue ends with Otto driving his bus across an icy bridge, believing that his complement is full of mannequins, when he is actually transporting real children. As his bus is close to tipping off the bridge, he comments that perhaps they will fall off slowly as in Inception; he is wrong and his bus falls into the river. The episode ends with the sound of Otto searching for his keys to let the children off the bus to swim to shore.