Frank Grimes, the new employee at the power plant, is displeased with Homer's incompetence and work ethic, and becomes further annoyed with this. He eventually declares himself an enemy of Homer. Meanwhile, Bart buys a factory for $1 and operates it along with Milhouse although they end up smashing it down and earn no money.
The show opens with a news report about Frank Grimes, an orphan who experienced many hard times in his life, and finally self-educated himself enough to enter the workplace. Mr. Burns sees the newscast and orders Smithers to hire him at the nuclear plant as Executive Vice President. The next day, Burns forgets this decision and gives the job to a courageous dog, and assigns Grimes to a low-level position. Shortly thereafter, Grimes crosses paths with Homer and doubts him. It may have something to do with the fact that Homer is lazy, annoying, and thoroughly unqualified for the job he has, yet he's so well off in life.
Meanwhile, while on a trip to a local government building, Bart wanders away from Marge and ends up buying an abandoned warehouse at a tax auction for a single dollar. He moves right in, and then hires Milhouse to act as a security guard.
Back at the plant, Grimes' dislike for Homer heats up as he furthers witness Homer's ineptitude. When he brings this up to Lenny and Carl, they see his point but say it's best not to think about it. When Homer accidentally almost drinks acid, Grimes' knocks the vial out of his hand and ends up wrecking the cafeteria wall, for which he then gets blamed by Mr. Burns after Homer, without mentioning Grimes saving him or his own carlessness with the vial, instantly points him out as responsible, and is given a second chance at his job, although a decreased salary. Grimes angrily approaches to Homer, confessing his hatred of him and declaring that they are enemies.
Upon advice from Moe, Homer decides to invite Grimes to dinner at his house to try and be friends. He has Marge prepare a lobster dinner and the family dress in their usual church clothes. However, when Grimes arrives he only gets angrier. This wasn't the life someone like Homer Simpson should have; he sees the house (he describes as a palace), the two cars, Bart owning a factory (he is thoroughly informed), Lisa having a high Intelligence level, his beautiful wife and learns of Homer's unlikely accomplishments (like becoming an astronaut, winning a Grammy, being on tour with the Smashing Pumpkins and being friends with ex-president Ford). Grimes rants that it's inconceivable that such a screw-up could achieve so much, when he worked hard for everything and the only thing he has to show for it is his briefcase, haircut and a tiny apartment between two bowling alleys (which impresses Homer). He says people like him are what's wrong with the country and that if he lived anywhere else he'd have starved long ago.
The next day Marge comforts Homer telling him that Frank doesn't hate him, he's just frustrated that life has always been hard to him while easy for Homer, and tells him if he cleaned up his act a little maybe Frank would be less hostile. After hearing this, Homer decides to clean up his act (in his own way), and appear more professional on the job but still neglects his workstation. Grimes still disapproves him, at break he once more tries to convince Lenny and Carl that Homer is an idiot but once more by pointing out that the number of accidents and meltdown have skyrocketed since Homer got his job, they clearly understand but say that it's best not to think about it. He says he would die a happy man if he could just convince them.
He decides to trick Homer into entering a children's contest "Design Your Own Power Plant" through a flyer by removing areas that show its juvenile theme. Homer decides to participate, unaware that it's for kids. Meanwhile, the warehouse Bart owns collapses in the middle of the night, leaving the rats to swarm Moe's tavern.
At the contest, Homer's diorama is a badly-created representation of the current plant, but with fins to improve air resistance and a racing stripe. Mr. Burns, impressed by his effort, awards Homer first prize, beating out Ralph Wiggum and Martin Prince, whose model was actually generating the power for the auditorium. His plan having backfired, a horrified and outraged Grimes ends up declaring the whole plant insane, and begins to rampage through the plant, imitating Homer as he loses his sanity. He goes around saying he's Homer Simpson, both mimicking and mocking his actions such as peeing on the toilet seat, eating like a slob, saying he's lazy and how these actions should be rewarded instead of punished because he's Homer Simpson. Grimes rushes into Homer's office, there he sees an extremely high voltage cable. Claiming he doesn't need safety gloves because he's Homer Simpson, he grabs the cable but ends up electrocuting himself to death, ironically committing suicide.
At the funeral, Reverend Lovejoy says that Frank liked to be called 'Grimey' and that even though he had many hardships, he would be looking down at the mourners with a smile. Homer gets the last laugh as he falls asleep during the funeral, drooling and muttering, "Change the channel, Marge." All the mourners and Lovejoy then laugh while the body of Frank Grimes is lowered down into the earth.