A naval commander is captaining a “huge, hurtling, eight-engined Navy hydroplane” through a terrible storm. Though his lieutenant fears he can’t make it, the Commander insists on full speed ahead, and the admiring crew expresses its faith in his abilities. Suddenly, Mrs. Mitty calls out a warning not to drive so fast, and it is revealed that the naval commander was part of a fantasy Walter Mitty has been having as he drives his car. As Mitty’s fantasy fades, Mrs. Mitty suggests that he see Dr. Renshaw for a checkup.
Walter Mitty drops Mrs. Mitty off at the hair salon in Waterbury, Connecticut. As she gets out of the car, she reminds him to buy a pair of overshoes, cutting off his protest that he doesn’t need them by saying, “You’re not a young man any longer.” Mitty puts on his gloves when his wife asks why he isn’t wearing them, but takes them off as soon as she has gotten out of the car and he is stopped at a red light, out of sight. When the light changes, a cop snaps at him to hurry, and Mitty puts the gloves back on before he drives away.
When he drives past the hospital, Mitty falls into another fantasy. A famous millionaire, Wellington McMillan, is suffering from “obstreosis of the ductal tract,” and the doctors performing his surgery—including Dr. Renshaw and two visiting specialists—need Mitty’s help. Mitty graciously accepts the specialists’ compliments, and saves the day when a machine breaks down by replacing a faulty piston with a fountain pen. However, before he can make his first cut, a shout from the parking-lot attendant interrupts the fantasy: Mitty has driven into the exit-only lane. Dazed, he tries to correct his mistake, but the attendant takes over, re-parking the car “with insolent skill.”
As he walks along Main Street, Mitty remembers another incident in which he had tried to remove his car’s tire chains, only to end up with them wound around the axles, and another “young, grinning garageman” had to come and help him. Ever since, Mrs. Mitty has made him drive to a garage whenever the chains need changing. Mitty plans to wear his right arm in a sling the next time he goes to a garage, so that the garageman will see that he couldn’t have taken the chains off himself and will not grin at him. Mitty then buys the overshoes, but has trouble remembering what else Mrs. Mitty told him to buy.
Hearing a newsboy shouting something about a trial, Mitty has a fantasy in which he is on trial for murder. When his attorney claims that he could not have committed the crime because his arm was in a sling, Mitty announces that he could have made the shot that killed the victim even with his left hand. As chaos breaks out in the courtroom, a beautiful woman appears in Mitty’s arms, and the District Attorney attacks her. Mitty punches him, calling him a “miserable cur”… which reminds him, back in reality, that he was supposed to buy puppy biscuit. A passing woman laughs at Mitty for saying “Puppy biscuit” aloud to himself. Though Mitty is already near a grocery store, he is embarrassed by the woman’s laughter and goes out of his way to request “some biscuit for small, young dogs,” at a smaller store further up the street.
Mitty makes sure to arrive first at the hotel where he will meet Mrs. Mitty after her hairstyling appointment, because she doesn’t like to get there before him. While he’s waiting at the hotel, he sees a magazine headline about whether Germany’s air force can conquer the world and imagines himself as Captain Mitty, a British fighter pilot. Mitty’s copilot is unable to fly, and so Mitty volunteers to fly alone. A young, deferential sergeant describes the danger of the mission and advises Mitty not to go, but Mitty (drinking several shots of brandy, to the sergeant’s admiration) speaks carelessly about the possibility of death. Just as Captain Mitty is leaving the dugout to get into the plane, Mrs. Mitty arrives at the hotel and scolds her husband for sitting in a hard-to-find spot and for not putting on his overshoes yet. In a rare moment of defending himself, Mitty asks, “Does it ever occur to you that I am sometimes thinking?” Mrs. Mitty says she will take his temperature once she gets him home.
On the way back to the car, Mrs. Mitty asks her husband to wait while she buys something at a drugstore. While he leans against the wall, he imagines he is standing before a firing squad. Scornfully saying, “To hell with the handkerchief,” Mitty bravely and proudly faces his imaginary death, describing himself as “Walter Mitty the Undefeated, inscrutable to the last.”