Bart brings Santa's Little Helper to school for "Show & Tell." When the dog disappears into the school's vents, Groundskeeper Willie is sent in to catch him. Soon, Willie is stuck inside the vents and both he and Santa's Little Helper must be rescued by the fire department. Superintendant Chalmers witnesses the debacle, fires Principal Skinner, and replaces him with Ned Flanders.

Bart feels responsible for Skinner's dismissal. When Skinner invites him to his home, the two become friends. Bart tells Skinner how the school is falling apart under Flanders's disciplineless regime.

Skinner re-enlists in the army. Missing his new friend, Bart plots to have Flanders fired and Skinner rehired by exposing Flanders's poor leadership. Chalmers is unfazed by the chaos. When he hears Flanders say "Lord" over the loudspeaker, Chalmers fires him for introducing prayer in the school. Skinner resigns from the army and is reinstated.