While tending his cigar store, middle-aged New Yorker Joe Gimlet runs into his boyhood friend, Ted Wright, now a prominent bank president. That night, Ted and his wife Elvina, who also grew up with Joe, dine with Joe and his wife Mary, another former resident of Corliss, Ted's home town. As the evening progresses, Ted, a longtime admirer of Mary, confesses to Joe that he envies his simple home life and offers his friend a chance to invest his $4,000 in savings in an aluminum underwriting scheme. Although Joe jumps at the idea, the more prudent Mary ignores her husband's pleas and refuses to part with the family savings. Determined to have his way, Joe gets drunk and insinuates to Mary that he would be a happier man if he had married the wealthy Elvina twenty years before. After Joe tells Mary that he will continue to drink until she says yes to Ted, he leaves the apartment reeling and is hit by a passing automobile. Joe wakes to discover that physically he is a young man again and is living with his mother in Corliss. Because he still has his middle-aged mind, however, Joe blurts out several facts about the future, causing his mother concern about his sanity. After the family doctor advises him to keep his crazy ideas to himself, Joe goes to his soda jerk job at the local pharmacy, where he encounters a young Elvina. When Elvina's rich father proposes to Joe that, if he wants to marry his daughter, he should invest his $400 in savings in a land investment scheme, Joe accepts the offer, remembering that in his prior life, he had said no. Although his engagement announcement crushes both his mother and Mary, who warns him that money cannot buy happiness, Joe goes ahead with his plan and marries into the Evans family. Guided by his knowledge of the future, Joe quickly becomes a millionaire, investing in such businesses as Henry Ford's automobile plant and the trucking industry, while Mary weds the more humble Ted. Joe also "predicts" the start of World War I and becomes known as an eccentric visionary. Moved by memories of his own post-war problems, Joe pledges $1 million of his profits to help the country's returning veterans. While Joe's generosity angers Elvina, President Woodrow Wilson hails Joe as a hero and offers him a job as the head of the War Industry Board. To avoid scandal, Joe drops plans to divorce the adulterous Elvina and throws himself into his new assignment. Joe's belligerent policies regarding war loans, however, eventually cost him his post and earn him Elvina's ridicule. Many years later, on the brink of the 1929 stock market crash, Joe goes into a cigar store and sees Ted working there. As before, the two couples dine together and talk about their lives. After Joe deduces that Mary is unhappy in her marriage, he offers Ted a chance to invest $4,000 in a safe venture, unaware that Elvina has secretly put all of their savings into the stock market. To Joe's surprise, Mary approves of the idea, causing Joe to make a reference about his poor judgment regarding love and money. Ruined by the stock market crash, Joe, who is now a bank president, denounces Elvina as a cheat and divorces her. On March 6, 1933, the same date of his automobile injury, Joe learns that his employees have plundered his bank and that he will be held accountable for their actions. No longer able to "see" into the future, Joe rushes to Mary and begs her to run away to Greece with him. After Mary tells him that she cannot leave Ted, Joe is pursued by a horde of policemen and, after a desperate chase, is apprehended. At that moment, Joe wakes up in his hospital room and is relieved to discover that Mary is still his loving if poor wife.