In 1923, Tate College freshman Harold Diddlebock Harold Lloyd is brought into his college's football team where he scores the winning touchdown, instantly catching the eye of the pompous advertising magnate J.E. Waggleberry. Although Harold dreams of becoming an “ideas man,” Waggleberry assigns him to a lowly bookkeeping position, setting a tone of unintended consequence that will echo through the years.
In 1945, the now middle-aged Harold is let go by Waggleberry for old age and not being an ideas-man. He is given an 18 karat Swiss watch and a severance check for $2,946.12, the remains of his company investment plan. He bids farewell to Miss Otis, a young woman who works at an artist's desk down the aisle, giving her the paid-for engagement ring that he had, having planned to marry each of her six older sisters (Hortense, Irma, Harriet, Margie, Claire, and Rosemary) when they had worked there before her. He wanders out, aimlessly through the streets, his life's savings in his trouser pocket.
Harold is approached by Wormy, a local con artist, petty gambler, and racetrack tout, who asks Harold for some money so he can place a bet. Jimmy Conlin as Wormy sees the large amount of cash that Harold has, and hoping to get him drunk enough to acquire some of the cash, takes Harold to a local bar for a drink. When Harold tells the bartender, Jake, that he has never had a drink in his life, the barkeep creates a potent cocktail he calls The Diddlebock. The effects of the alcohol cause Harold to yowl uncontrollably. Gazing at himself in the bar mirror, Harold suddenly declares himself a loser and races out to remake himself. Soon Harold is getting his hair cut and his nails manicured at a local tailor shop and salon, and is trying on a gaudy plaid suit supplied by Formfit Franklin Franklin Pangborn.
In the midst of his transformation, Harold overhears Wormy talking with his bookie Max Lionel Stander, and impulsively bets $1,000 of his money on a 15-to-one long shot horse named Emmaline. To everyone's surprise, Emmaline wins, and the now-rich Harold celebrates all around town on a day-and-a-half binge of spending, gambling, and carousing.
Days later, Harold wakes up on the sofa inside the house of his widowed sister Flora. She chastises him for his behavior. He is hungover, and finds he has a garish new wardrobe and a ten-gallon cowboy hat. Unable to remember much about his drunken binge, Harold goes to return the plaid suit and is surprised to learn that he now owns a horse-drawn cab, complete with an English driver named Thomas.
A worried Wormy then rushes up and informs Harold that, with winnings from a second bet, Harold also bought a bankrupt circus. Harold and Wormy visit the circus-loving Wall Street banker Lynn Sargent, but he turns them down because he is trying to unload his own bankrupt circus. When the rest of the town's bankers follow suit, Harold comes up with an idea. To get past the bank guards, Harold dresses up in his plaid suit and brings along Jackie, a tame circus lion, who incites panic. Carrying a filled Thermos, Wormy gives shot drinks of the potent Diddlebock cocktail to each of the bankers they visit so their inhibitions will fade and convince them to put in bids for ownership of the circus.
Harold, Wormy, and Jackie the Lion are arrested and thrown in jail. Miss Otis bails them out the following day. They find that the publicity has attracted a mob of bankers at the jail who want to buy the circus – but Ringling Brothers outbids them. Harold celebrates with another Diddlebock, and again has another relapse. Harold wakes up days later in the horse-drawn cab with Miss Otis, where he learns that he received $175,000 for the sale of the circus, he is now an executive at Waggleberry's advertising agency, and that he and Miss Otis are married. Reassuring Harold that she truly loves him, Miss Otis gives him a big kiss.
