After Homer realizes he has lived exactly half the average life expactancy, he falls into a deep depression. The family tries to cheer him up by showing him home movies of his varied accomplishments. When the film, breaks, Homer wants to find out who's to blame for inventing movies. Lisa explains that Thomas Edison invented movies, along with lightbulbs and a host of other important products. Homer does a little research, and soon, all he can talk about is Thomas Edison.

He quits his job and starts an inventing career. His first attempts at creating new products fail miserably, and his depression returns. At the dinner table, while leaning back in his chair, Homer nearly falls over backwards. At the last moment, he's caught by the extra legs he hinged on onto the back of his chair during his inventing spree. His family tells him that he's finally come up with a good idea.

Telling his inspirational poster of Edison about his successful invention, Homer discovers from the picture that Edison himself is sitting on a six-legged chair. Homer realizes that Edison may not have told anyone about the chair, and he and Bart travel to the Edison Museum to destroy the evidence so he can take the credit. About to smash the chair with one of his failed inventions, an automatic hammer, Homer sees a chart Edison made comparing his achievements to da Vinci's. It's strikingly similar to a chart Homer has in which he compares himself to Edison. Homer realizes that he and Edison are kindred spirits and decides he can't destroy the chair. Later the automatic hammer Homer left behind and the six-legged chair are discovered in the museum, Edison gets credit for the ideas, and his heirs stand to make a fortune.