When reporter ANN MITCHELL is laid off by managing editor HENRY CONNELL because of streamlining, she begs to stay on since she's supporting her MOTHER and TWO SISTERS, but it's no use. Angry, she gathers up her belongings but then, as a parting shot, types up a fake letter from "John Doe" stating that he's so downtrodden by the unfairness of things that he intends jumping off the building on Christmas Eve.
The paper prints the letter and it causes a sensation. Everyone relates to and wants to help John Doe. Connell, desperate to get hold of the original letter is shocked when Ann tells him there was no letter. Connell, angry, is ready to print a retraction but Ann suggests that they hire a "fake John Doe" to embody the pathos of the letter. She gets her job back along with a lucrative fee and contract.
Several desperate MEN line up claming to have written the letter, so Ann and Connell must now pick the one. When handsome JOHN WILLOUGHBY walks in, Ann's clearly smitten. A likeable, quiet baseball player who's fallen on bad times, John's the one who will become "John Doe." Although he seems too honest to lie, Ann believes he's desperate enough. They create a fake letter, put him up at a fancy hotel with bodyguards, making him sign an agreement. Also in tow (much to Connell's chagrin) is THE COLONEL, a confirmed vagabond, distrustful of society, who warns John that he's falling into a trap of privilege.
Next come publicity photos, which are directed by Ann to get the correct "angry protest" look. With headlines proclaiming his anger at the unfairness of the world, John becomes an increasing media sensation, courtesy of hyperbolic headlines concocted by Connell. Meanwhile, the GOVERNOR suspects John Doe is a myth but mistakenly feels it was concocted by publisher B. D. NORTON to discredit him. Ann convinces Norton to play it for what it's worth. Norton offers her money to write radio speeches to sell Doe. He also wants her to work directly with him and not Connell.
Ann goes to work, typing up a storm but nothing comes to mind. Ann's Mother suggests that she write something upbeat and simple, using the values of Ann's late father as an inspiration. By now, John has begun realizing that his baseball career might not get started again if the John Doe business is revealed as a phony.
Nonetheless, John reads his first manufactured upbeat speech, written by Ann to a packed house. Ann coaches him to be sincere, suggesting that she's fallen in love with John Doe. The speech, broadcast on the radio, stirs the people with its "love thy neighbor"-style message. CROWDS love him but John can't get away fast enough. He and the Colonel resort to the boxcars and flee. B. D. Norton, thinking he was great, wants him located.
When a DINER WAITER recognizes him, John's hope for a return to normalcy is squelched by sudden CROWDS, eager to meet him. Ann and Norton locate him. John isn't happy about it. When Norton offers him a lecture tour, he refuses it angrily. When the common PEOPLE who have a "John Doe" club talk to him, however, he softens when hearing how he's touched them. Now, John's torn. His itinerant pal, The Colonel, thinks he's been "hooked" and, disgusted, walks out on him.
Norton arranges the lecture tour. John speaks in state after state, addressing the many national clubs in his name. Connell tells Norton, however, that he's curious why Norton is spending so much money on the tour. In the meantime, Ann, knowing that John now likes her, feels increasingly like the heel she feels she is. She feels even worse when John relates a tender dream that he had about her and talks to her about how he relates to the lonely, hungry people to whom he's been speaking.
Norton gives Ann a fur coat and a gift. He then tells her that he wants John Doe to announce a new "third political party," which, it's clear to Ann, was Norton's plan all along. Norton wants to be the presidential candidate for that party, which will be less for the people than it is for those like Norton - big business types. John visits Ann's Mother, telling her he'd like to marry Ann. Her gentle advice is just to ask.
While John talks with Connell, the editor, who's had a few drinks, blurts that Norton has a dark agenda. John feels hurt and used, as he'd felt the whole John Doe was legitimate, not a tool for Norton's political ambitions. Connell also tells John how well paid Ann is to write the speeches and would do anything for money. Angry, John walk in on Norton and Ann at a lavish dinner party he's having in his mansion. John overhears Norton's political plotting as well as his toast to Ann for having aided him. Ann sees that John is listening.
John asks Ann if indeed she wrote Norton's speech and she admits it. John then confronts Norton and all at his party. John threatens to thwart his efforts. Norton accuses John of being the fake, not him. Norton threatens to reveal such if he talks. Aghast that Norton would kill the John Doe movement to protect his own interests, John is furious with all of them. He tells them off with passion, impressing Ann and the STAFF, who overhear. John feels that the movement is far too powerful for Norton and his cronies to stop.
Norton wants John stopped before he can blow the whistle at the huge gathering that has now formed at a public arena. Ann catches up with John, trying to explain, telling him that she didn't know what Norton and his people were dong. John doesn't believe her and doesn't allow her to accompany him in his cab.
John shows up at the event as a huge CROWD stands in the rain singing the National Anthem. A PRIEST introduces John. Before he can speak, Norton has published a report that John Doe is a fake. Norton's TROOPERS storm the event as John tries to get the mob's attention and speak. With John subdued, Norton takes the mike and accuses him of being a fraud. As John tries to speak, the Troopers cut the mike cords. Ann listens on the radio as the mob becomes unruly. John returns to his place beneath a bridge with The Colonel.
Newspapers herald his fakery. Clubs disband. John feels disgraced. He's tortured by memories of the sweet, simple people that he feels he now let down. Christmas Eve comes, the appointed time that John Doe was to take his life by leaping from the building. Some of his FOLLOWERS are convinced he'll jump, so they head for the roof, as does Ann.
Indeed, John shows up, a letter in his hand addressed to the admirers he feels he let down. He's about to jump when Norton steps from the shadows with this MEN, telling him that if he jumps the mayor has been instructed to remove his i.d. and thus his suicide will be for nothing. But John tells him he's already mailed a copy of the letter elsewhere. John's glad they're here. He tells Norton that the movement that they killed will be born all over again. Ann shows up as he's about to mump, begging him not to do it. She insists they can start it over again together. His followers agree. John and Ann walk away. Connell gets in the last word with a thwarted Norton.