At Will Bloom’s wedding party, his father Edward recalls the day Will was born, claiming he caught an enormous catfish using his wedding ring as bait. Will, having heard these stories all his life, believes them to be lies and falls out with his father. Three years later, Edward is stricken with cancer, so Will and his pregnant French wife Joséphine return to the town of Ashton, Alabama to spend time with his father. During the plane ride, Will recalls a story of Edward’s childhood encounter with a witch, who shows him his death in her glass eye. Edward, in spite of his illness, continues to tell the story of his life to Will and Joséphine. He claims to have once been bedridden for three years due to his rapid growth spurts. He then became a locally famous sportsman before being driven by his ambition to leave his hometown. He sets out into the world with a misunderstood giant, Karl, who was terrorizing the town by eating livestock from the surrounding farms. Edward and Karl find a fork in the road and travel down separate paths. Edward follows a path through a swamp and discovers the secret town of Spectre, the cheery locals claiming he was expected. There, he befriends Ashton poet Norther Winslow and the mayor’s daughter Jenny. However, Edward leaves Spectre, unwilling to settle down but promising Jenny he will return.
Edward and Karl reunite and visit the Calloway Circus, where Edward falls in love with a beautiful woman. Karl and Edward get jobs in the circus, where the ringmaster Amos Calloway reveals to Edward one detail about the woman at the end of every month. Three years later, Edward discovers that Amos is secretly a werewolf and is attacked by him, but avoids getting him shot with a silver bullet by playing fetch until he turns back into human in the morning. Amos, upon returning to normal, reveals the woman’s name to be Sandra Templeton, and that she attends Auburn University. Edward goes to Auburn via cannon, and stalks Sandra for many days, even going so far as to plant millions of daffodils outside of her dorm bedroom. She finally tells him that she is engaged to Edward’s childhood peer Don. Don brutally beats up Edward, prompting Sandra to break off their engagement and marry Edward; not long after, Don soon dies of a heart attack as the witch had prophesied. Shortly after, Edward is conscripted into the army and sent to fight in the Korean War. He parachutes into the middle of a North Korean military show, steals important documents, and convinces Siamese twins Ping and Jing to help him go home in exchange for making them celebrities. Upon returning home, Edward becomes a travelling salesman and crosses paths with Winslow. He unwittingly helps Winslow rob a failing bank with no money and later inspires the poet to work on Wall Street. Winslow becomes a wealthy broker and repays Edward with a large sum of money, which Edward uses to obtain his dream house.
In the present, Will investigates the truth behind his father’s tales and travels to Spectre. He meets an older Jenny, who explains that Edward rescued the town from bankruptcy by buying it in an auction and rebuilt it with help from his friends from Calloway Circus. Will suggests that Jenny had an affair with his father, but she reveals while she loved Edward, he remained loyal to Sandra. Will returns home but learns Edward has had a stroke and stays with him at the hospital. Edward wakes up but, unable to speak much, asks Will to narrate how his life ends. Though struggling, Will tells his father of their imagined daring escape from the hospital to the nearby river, where everyone from Edward’s past is there to see him off. Will takes Edward into the river, where he transforms into the giant catfish and swims away. A satisfied Edward dies, knowing Will finally understands his love for storytelling. At the funeral, Will and Joséphine are surprised when all the people from Edward’s stories come to the service, though each one is a slightly less fantastical version than described. Will, finally understanding his father’s love for life, passes on Edward’s stories to his own son.