|Spencer Tracy||Thomas A. Edison|
|Rita Johnson||Mary Stilwell|
|Lynne Overman||Bunt Cavatt|
|Charles Coburn||General Powell|
|Gene Lockhart||Mr. Taggart|
|Henry Travers||Ben Els|
|Felix Bressart||Michael Simon|
Thomas Edison is an enterprising young inventor hungry for achievement. After he sells a version of the stock market ticker that he has perfected, Edison uses the money to open an ''invention factory,'' where he works on projects like the phonograph. When one of his friends boasts that Edison has invented an electric light before any such object exists, Edison must use all of his skill to complete the task, relying on innovation and trial and error.