In a bustling neighborhood of Mexico City, a friendly and clumsy mailman named Mario faces the daily problems of life with his characteristic humor. Everything changes when a famous boxing promoter mistakes him for a professional boxer due to his unusual ability to dodge punches, leading him into a series of comedic situations. Unintentionally, Mario becomes the sensation of the ring, gaining admirers and outsmarting his rivals with his wit and cleverness.
As his boxing career takes off, Mario also becomes embroiled in a deeper plot when he falls in love with a beautiful young woman, who turns out to be the daughter of the boxing champion he must face in an upcoming match. As the big fight approaches, Mario has to deal with the pressures of becoming an idol while also staying true to his principles and his heart.
With a mix of slapstick, wordplay, and the endearing personality of Cantinflas, this comedy delves into the world of boxing, but never loses sight of the message that true courage is not measured solely in punches, but in integrity and loyalty. With a touch of romance and an endless array of hilarious situations, Mario must discover what it really means to fight, both inside and outside the ring.