Based on James Thurber's story, a magazine writer imagines himself a hero while he becomes involved in a search for a book desired by murderers.
While Walter Mitty (Danny Kaye) is driving, his mother Eunice Mitty (Fay Bainter) nags him and asks him to buy Sea Drift soap. Walter imagines he is a captain of a ship in a storm. Walter works for publisher Bruce Pierce (Thurston Hall), who asks for stories on hospital love stories. Walter imagines he is a doctor admired by a pretty nurse.
Eunice asks Walter if he got everything she requested. His fiancée Gertrude Griswald (Ann Rutherford) comes for dinner with her mother and dog. Walter lights a fire with a newspaper and sees himself flying in the war. In the officers' club he satirizes a music professor and sings about a symphony.
On a commuter train Rosalind van Hoorn (Virginia Mayo) pretends Walter is her husband to escape from a man. In a cab she asks Walter to help her. He realizes he is late but forgets his briefcase and follows her. A man that Rosalind meets is stabbed to death. Walter reports it to the police, but they are gone.
Later Rosalind takes Walter to her uncle Peter van Hoorn (Konstantine Shayne), who warns him he is in danger because of a book that lists the treasures of the Dutch government stolen by the Nazis. Walter finds that he has the book and puts it in a corset and flees from a man. Dr. Hugo Hollingshead (Boris Karloff) brings Walter a manuscript on homicide. Hugo takes a book and pushes Walter out the window. Walter climbs in Pierce's window again.
While playing bridge with Gertrude's family, Walter imagines he is a Mississippi gambler. Walter tells Rosalind about the book, and she hides it in her uncle's desk. Walter faints. When he wakes up, Peter says he has no niece. Pierce and Eunice take Walter to Dr. Hollingsworth for psychiatric treatment. Walter imagines he is a western hero winning a fight.
Walter goes to rescue Rosalind from an estate. She says that her uncle is the Boot. Walter is caught in his own trap, but the police arrive and help him. Walter tells off Pierce and Gertrude's family. In the final scene Pierce shows Rosalind and Walter his new office.
This farce uses a plot device derived from the crimes
of World War II while displaying Danny Kaye's comedic talent.
The imagination of Walter Mitty explores the grandiose fantasies
that common people often have.