A group of eight scholars, all bachelors except for one widower, reside together in a spacious New York City home, dedicated to the ambitious task of compiling a comprehensive encyclopedia of human knowledge. This endeavor has been their focus for several years, with one member confidently stating that they are only three years away from completion. The youngest among them, Professor Bertram Potts, specializes in modern American slang and is brought to life by Gary Cooper. Overseeing their scholarly pursuits is their strict housekeeper, Miss Bragg, portrayed by Kathleen Howard, who ensures that the professors work in a disciplined and somewhat secluded environment.
Supporting this academic endeavor is Miss Totten, played by Mary Field, whose late father, Daniel S. Totten, originally funded this project with a hefty $250,000. His motivation stemmed from his irritation at not being acknowledged in the Encyclopedia Britannica for inventing the electric toaster. However, now that the funding has run dry, Miss Totten is reluctant to invest her own money. Despite this, she harbors a soft spot for Potts, which complicates matters as the urgency to complete their work grows.
The situation takes a turn when a garbage man seeks assistance from the professors for a quiz contest. This prompts Bertram to realize his outdated knowledge of slang, leading him into a vibrant nightclub scene where he becomes captivated by the slang in the song "Drum Boogie," performed by Gene Krupa's band with the enchanting vocals of Barbara Stanwyck as Katherine "Sugarpuss" O'Shea. At the conclusion of the performance, Sugarpuss finds herself needing a place to hide from the police, who are on the lookout for her mobster boyfriend, Joe Lilac. Initially hesitant, she soon recognizes that Potts is her only chance of evading the law. She seeks refuge in the professors’ home, despite Potts’ protests and Miss Bragg's threat to resign over her presence.
Meanwhile, Joe, depicted by Dana Andrews, has plans to marry Sugarpuss, influenced by the notion that their marriage would prevent her from testifying against him. The professors quickly grow fond of Sugarpuss, and in turn, she starts to bond with them, teaching them to conga and conveying the meaning of "yum yum" (kisses) to Bertram. However, her initial interest in Potts is merely a tactic to maintain her cover until she can escape to New Jersey with aid from Joe's henchmen.
Despite her plans, genuine feelings between Sugarpuss and Potts begin to surface, leading to a marriage proposal from him, which she skillfully evades. As their escapade unfolds, Miss Bragg uncovers Sugarpuss's intentions but is knocked out by Sugarpuss, allowing them to attempt their journey to New Jersey. However, fate intervenes when their car breaks down, forcing the group to stay at a motel. Joe and his henchmen arrive, revealing the marriage plot to Potts, who is heartbroken. Yet, when the police show up alongside Miss Bragg, Potts chooses to protect the professors rather than betray Sugarpuss.
Back in New York, Potts voices his remorse for the distractions caused by Sugarpuss and suggests they must work harder to catch up. A twist occurs when one of the professors reveals that Sugarpuss had given him an engagement ring, which turns out to belong to Joe, indicating her true feelings for Potts.
Just as things seem dire, Miss Totten returns with her lawyer, threatening to end the project due to negative publicity. Potts argues for his dismissal while advocating for the remaining professors to continue their valuable work. Before a resolution is reached, Joe's henchmen invade their sanctuary, demanding their cooperation.
Simultaneously, at the Justice of the Peace, Sugarpuss is torn, contemplating marriage to Joe while harboring affection for Potts. Upon realizing the danger posed to the professors, she understands the stakes of her decision. With clever conversation, the professors ingeniously distract the henchmen, eventually overpowering them and learning of the impending wedding through a humorous interrogation involving tickling.
They make a dramatic arrival just in time to halt the ceremony. Potts challenges Joe to a fistfight, although his initial attempts falter. Fortunately, the arrival of the police turns the tide, leading to the capture of the villains. Back at the Justice of the Peace, Sugarpuss expresses self-doubt about deserving Potts. In a tender moment, he shows her that she most certainly does, sealing their connection with a bit of "yum yum."
