The Devil and Miss Jones (movie, 1941)

The wealthiest man in the world, John P. Merrick, is a private person who likes to stay anonymous. One of his many assets is Neeley's Department Store. There is labor unrest at the store, and the employees' anger is directed at him, who they hang in effigy outside the store despite not knowing what he looks like. Merrick, not happy at what he sees going on, decides to mete out the rabble-rousers. So he goes undercover as a sales clerkin the shoe department.