Years ago, Principal Skinner and Gary Chalmers received a government grant to improve the school. Later, Agnes Skinner then did the laundry of Skinner's pants that contains the money. Skinner and Chalmers then build the phony schoolrooms with rented children mannequins and took photos of it not to let fed come after them. However, they had to return the mannequins by 5:00, so Otto drove with them. He drove across an ice bridge when the bus fell into the icy water. Otto then thought that he killed 24 children.
Nowadays, Lisa found the secret room that looked like five classrooms in one, but where everything was fake. She then saw a hooded figure write "The Children are on Bus 23" on the blackboard. Lisa and Bart visited Nelson who had heard Skinner and Chalmers talking about Bus 23. Nelson thought it is full of children going for a field trip, but a bickering ensued: Skinner believed the bus was too heavy to cross the ice bridge ahead, but Chalmers stated that "there's no time to be safe." Left with no choice, Skinner sicced the bus away from the school with banging, and "that bus never came back."
Homer took Bart and Lisa in his Duff Blimp above the river. However, Lisa fell down into it and saw the bus full of children mannequins. Homer jumped there to save her, but the mannequins covered the water top, trapping Homer and Lisa under them. Suddenly, The Pooter Toot Express appeared and hit into the tree that fell on the river, letting Homer and Lisa out. Skinner and Chalmers then explained them what had really happened to Bus 23.