When he loses his job, a middle-aged bookkeeper goes out on the town.

After Harold Diddlebock, a bumbling freshman water boy, scores the winning touchdown for his college's football team, he is approached by alumnus E. J. Waggleberry. In the excitement of the moment, Waggleberry, an advertising tycoon, offers Harold a job upon his graduation, but when Harold appears in the executive's New York office four years later, Waggleberry fails to remember him. Although Harold dreams of becoming an "ideas man," Waggleberry assigns him to a lowly position in the bookkeeping department. Twenty-two years later, the platitude-spouting Harold is still working as a bookkeeper when he is fired by Waggleberry for incompetency and lack of ambition. Before leaving the agency, Harold collects his life savings and confesses to Miss Otis, an artist with the firm, that he is in love with her. Recalling her six older sisters, all of whom he fell in love with but never proposed to, Harold then gives Miss Otis the engagement ring he bought for her eldest sister years before. Later, on the street, a depressed Harold is studying the classifieds when Wormy, a racetrack tout, asks him for four dollars. After Harold hands the pesky Wormy a large bill, Wormy, sensing an opportunity, insists on taking his sad "friend" to a bar. There bartender Jake concocts a special drink for Harold, who has never imbibed alcohol. The drink, which Jake proudly dubs "The Diddlebock," emboldens Harold and causes him 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, and is trying on a gaudy suit supplied by tailor Formfit Franklin. In the midst of his transformation, Harold overhears Wormy talking with Max, a bookmaker's assistant, and impulsively bets $1,000 on a long shot named Emmaline. To everyone's surprise, Emmaline wins, and the now-rich Harold begins to celebrate all around town. Sometime later, Harold is awakened at home by his widowed sister Flora, who chastises him for his wild, irresponsible behavior and hideous clothes. Unable to remember much about his drunken binge, particularly about what he did on Wednesday, Harold wanders outside and is surprised to learn that he now owns a hansom cab and employs 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. To feed the circus' starving lions and tigers, Harold first seeks help from the Kitty-Poo Home for Cats, then gets the idea to sell the circus to Wall Street banker Lynn Sargent. Although circus lover Sargent reveals that he, too, is trying to unload an unprofitable bigtop, Harold immediately comes up with another scheme. With Jackie, a tame circus lion, in tow, Harold and Wormy visit other bankers and suggest that, to improve their public image, they invest in a free circus for children. Jackie's presence causes a screaming panic, and soon Jackie, Harold and Wormy end up on the ledge of a skyscraper window. After nearly falling to their deaths, the trio is arrested and thrown in jail. As hoped, Harold's picture appears in the newspaper, but it is Miss Otis, not the bankers, who comes to bail him out. When Thomas then reveals that the newspaper listed the wrong police station in its story, Harold and Wormy rush to the other station and are relieved to see a mob of bankers there. The bankers bid desperately on the circus, but are quickly outbid by a representative of the Ringling Brothers circus. To celebrate, Harold downs a "Diddlebock," and sometime later, finds himself in his cab with Miss Otis. Although Miss Otis informs him that he received $175,000 for the circus and has been made an executive at Waggleberry's firm, Harold notices that she is wearing a wedding ring and becomes depressed. Miss Otis then reveals that, during his last "Diddlebock" binge, he married her. Reassuring Harold that she truly loves him, Miss Otis gives him a big kiss, and Harold finally remembers what he was doing on Wednesday.