When a traveling carnival rolls into a small farming town, chaos ensues as many of the local residents feel cheated by the carnival's tricks, leading to a wave of anger and destruction. Bill Hogan, the carnival promoter, realizing that their debts are mounting and that trouble is inevitable, heads to the nearby bank to secure funds to escape before the carnival's financial woes catch up to them. There, he notices that instead of a traditional adding machine, the bank employs a meek clerk named [Edmund Gwenn as Jeffrey Crane](#/actor/edmund-gwenn), who possesses extraordinary calculating skills. Recognizing an opportunity, Hogan hires him as "Chain Lightning" and puts him on display, challenging him against an adding machine, aiming to impress the crowd and secure their reputation. However, the townspeople show little interest, and things take a turn for the worse when the local sheriff steps in and seizes the carnival’s assets, effectively shutting it down.
In the wake of this setback, Bill decides to seek a fresh start by traveling east with his girlfriend, [Betty Furness as Kitty Crane](#/actor/betty-furness), and her father, Jeff Crane, the carnival's alcoholic owner, played by [Edmund Gwenn](#/actor/edmund-gwenn). During their journey, they also take along Elmer Lamb, the gentle and unassuming clerk, who has a special fondness for the three dairy cows he's been allowed to visit. Elmer, shy and unassuming, quickly becomes enchanted with Kitty, whose charm and kindness catch his heart.
On the train, they are joined by J. Montgomery Brantley, a renowned bridge champion, eager for a game. Although Elmer has played whist, he's never tried bridge, and the other players hesitate to include him because he always wins. Encouraged, Elmer agrees to play against Brantley, initially with just 10¢ as stakes. To everyone's surprise, Elmer wins several hands, and his winnings rapidly accumulate, as his understanding of the game translates into earning a sizable sum—much to the shock of those around him. His incredible talent soon becomes a source of public interest, and a scandal erupts when the newspapers reveal Brantley's unexpected defeat, risking Brantley's reputation as a master bridge player.
This sets the stage for a nationally broadcast challenge: fifty rubber matches over eight days, with a grand prize of $15,000. As Elmer begins to fall behind, he finds his footing and starts to lead. However, danger lurks; gangsters, envious of his success, conspire to bribe him into losing the crucial matches. These criminals kidnap Elmer on the final day, seeking to manipulate the outcome. Fortunately, Elmer is rescued just in time, but in the commotion, Jeff accidentally strikes him over the head, causing his remarkable calculating powers to disappear.
Desperate to restore Elmer's abilities, Jeff tries to hit him again, but this only worsens his condition. Seeing no other options, Jeff suggests that Kitty pretend to genuinely love Elmer temporarily. Though reluctant at first, she goes along with the plan, and surprisingly, Elmer's brilliance returns. Empowered, Elmer wins the pivotal match, earning the victory and the prize money. Yet, as he basks in his triumph, Jeff reveals that the deception was a ruse, leaving Elmer heartbroken and feeling betrayed.
Meanwhile, Kitty begins to realize she truly loves Elmer, and she breaks up with Bill Hogan. When Elmer returns to his bank, he finds that he has been replaced by an adding machine, symbolizing how much he's been overlooked and undervalued. Still, he finds solace in visiting his beloved cows, which remain faithful companions, and to his surprise, Kitty arrives—and she is not alone. She has used the winnings from his victory to purchase the farm himself, indicating her genuine affection and intentions.
Throughout this charming story, themes of kindness, talent, and love emerge, as a humble man with extraordinary abilities finds himself at the center of a whirlwind of deception, challenge, and ultimately, hope and genuine connection. The film portrays a heartwarming journey of self-discovery, showing that sometimes, the simplest people can surprise the world with their hidden talents and their capacity for love.
