The worker's contract at the power plant is up for renewal, and the union prepares to deal with Mr. Burns. Meanwhile, Lisa finds out from her dentist she'll need braces.
While reviewing the proposed contract, which includes a green cookie on St. Patrick's Day, Mr. Burns remembers how workers were treated in the early part of the 20th century. Burns wants to relive those days and decides to take away the company dental plan.
At the union meeting, everyone votes in favor of the new contract. Even though it means giving up the dental plan, they get a keg of beer in exchange. Homer realizes he'll have to pay for Lisa's braces and urges everyone to fight Burns for a better contract. Homer is elected union president.
While Homer negotiates with Burns, Lisa has to wear an antiquated set of braces that predate stainless steel. In an effort to subdue the people of Springfield, Burns cuts off the town's power and awaits their reaction in a Grinch-like pose on his balcony. He hears the workers singing outside the plant in a united effort and Burns realizes he can't win. He agrees to give back the dental plan as long as Homer resigns as union president. Homer does the Curly shuffle and Burns realizes Homer wasn't the brilliant tactician he thought.
Lisa's new braces are almost impossible to see and everyone lives happily ever after.