Woodrow LaFayette Pershing Truesmith sits disconsolately at a bar with his beer. When six Marines, led by Sgt. Julius Heffelfinger, come in, Woodrow buys them all beer because they are short on cash, and the grateful Marines, recently returned from the battle at Guadalcanal, introduce themselves. The soldiers learn that Woodrow's father, also a Marine, died a hero in World War I on the same day that Woodrow was born, and that Woodrow's lifelong dream is to follow in his father's footsteps. Humiliated by his dismissal due to chronic hayfever which occurred over a year before, Woodrow reveals that he wrote to his mother that he was sent overseas, and has not been home since. "Sarge" recalls that Woodrow's father was his own sergeant during World War I, and that he was present the day Truesmith died on the battlefield. Bugsy Walewski, a tough but compassionate Marine who believes that mothers are sacred, is appalled that Woodrow would allow his mother to think that he is in combat, and immediately telephones Woodrow's mother in Oakridge, California. Bugsy impersonates an officer and informs her that Woodrow is a hero and is returning home from Guadalcanal. Led by Sarge, the Marines then escort Woodrow to a train headed for California, and force him to wear his uniform, even though he believes it is against regulations. They then insist on giving him several of their own medals, believing that he will be able to slip quietly into town, impress his mother, and then discard the uniform. Woodrow is mortified when the entire town and four marching bands greet him at the Oakridge train station, and the mayor gives him the key to the city. Woodrow immediately regrets his deception, but the Marines continue to hail him as a hero. Woodrow's former girl friend Libby, whom he had written and told not to wait for him, is now engaged to Forrest Noble, scion of the wealthiest family in town, but is waiting for an appropriate time to tell Woodrow the news. That night, the town's elder citizens, led by Judge Dennis and mayoral candidate Doc Bissell, nominate a stunned Woodrow for mayor. Without actually revealing his deception, Woodrow proclaims his unworthiness, but the supportive crowd that has gathered outside his house thinks that he is only being humble. Forrest's father, a mayoral candidate himself, fires Libby as his secretary after she defends Woodrow in the face of his own character defamation. As Woodrow's campaign supporters celebrate with fervor, Woodrow drinks cooking wine and contemplates his ruin. Libby finally confesses her impending marriage to Forrest, and Woodrow calmly accepts the news as he fears she might be hurt when the truth about him comes out. Woodrow insists he is a phony, but Libby is brokenhearted that he will not fight for her. Noble's political boss, meanwhile, becomes suspicious of Woodrow and cables the Marines for verification of his status. The next morning, in order to avoid the campaign, Woodrow pretends that he has been called back into active service. Bugsy sees through his ruse and loses respect for Woodrow. Woodrow participates in the campaign parade that leads him to the town hall, where Noble and his boss are eager to spread the news of Woodrow's medical discharge. Woodrow unexpectedly confesses to the fraud in an eloquent speech, however, and Bugsy's faith in him is restored. Woodrow then returns home to pack, and Libby, realizing that Woodrow is truly courageous because of his ability to face the truth, breaks off her engagement with Forrest and insists on joining Woodrow in his travels. While they are waiting at the train station, a mob led by Sarge approaches. Afraid of a lynching, the Marines protect Woodrow, but Judge Dennis and Doc Bissell announce that after careful consideration, they still want Woodrow to run for mayor because of his courage and veracity. Noble faints when he hears the news, and after accepting the nomination, Woodrow bids farewell to his devoted Marine friends.