Ahí está el detalle

The boyfriend (Cantinflas) of the servant of a rich industrial man gets into the house in order to kill a mad dog. Suddenly this man appears so the servant tells him that Cantinflas is his wife's brother (Francisco Jambrina), who had been lost for years. The rich man then remembers that his father in law's testament could only be paid when all brothers get together, so treats Cantinflas, a real bum, as a king.