At Will Bloom's (Billy Crudup) wedding celebration, his father Edward, portrayed by Albert Finney as Old Edward and Ewan McGregor as Young Edward, shares a fantastical tale about the day Will was born, claiming he once hooked an enormous catfish using his wedding ring as bait. Will, having heard these extravagant stories throughout his life, is skeptical and ultimately distances himself from his father. However, three years later, with Edward diagnosed with cancer, Will and his pregnant French wife, Joséphine (Marion Cotillard), return to their roots in Alabama to spend precious moments with Edward.
Edward's life unfolds through a series of vivid flashbacks, starting with his fateful encounter with a mysterious witch in his hometown of Ashton. She reveals to him a vision of his death, yet Edward faces the revelation without fear. As he matures, Edward finds the confines of his hometown restrictive, as he feels like a freak with his rapidly growing body, often mocked at school. Despite this, he excels academically and athletically in middle school. Seeking adventure, he befriends a misunderstood giant named Karl (Matthew McGrory), who joins him after arriving with a traveling circus. When townsfolk deem Karl a monster, Edward courageously volunteers to communicate with him, persuading Karl that a small town like Ashton cannot contain their ambitions. Together, they embark on a journey to the bustling cities beyond.
As they reach a fork in the road, Edward and Karl part ways, with Edward wandering through a swamp and eventually stumbling upon the idyllic town of Spectre, where the cheerful residents insist they were expecting him. There, he forms a bond with Norther Winslow (Steve Buscemi), a local poet, and the mayor's daughter, Jenny (Helena Bonham Carter). Though he promises Jenny that he will return, Edward cannot bring himself to settle down in Spectre.
In the present, Joséphine, speaking to Edward in his hospital bed, prompts him to recount the story of how he met his beloved wife, Sandra. With Will eavesdropping outside the door, Edward dives back into his memories. After reunifying with Karl, the duo finds themselves at the Calloway Circus, where Edward falls head over heels for a captivating woman. Ringmaster Amos Calloway (Danny DeVito) engages Edward by sharing tantalizing details about the woman at the end of each month, all while Karl remains a key performer.
Three years later, Edward learns that Amos has a secret—he’s a werewolf—yet bears no malice towards Edward. Upon learning the woman he loves is Sandra and a student at Auburn University, Edward confesses his feelings. Unfortunately, Sandra declines his marriage proposal as she is already engaged to Don Price (David Denman), another Ashton native. After a physical confrontation with Don, which Edward agrees to handle without harm to Don, Sandra chooses to break off her engagement and marry Edward instead.
Edward is soon drafted into the army and deployed to fight in the Korean War. Gritting his teeth through a three-year service, he deliberately seeks perilous missions to cut the time down to one year. His escapades include a daring parachute drop into the enemy territory, stealing crucial documents, and convincing the Siamese twins, Ping and Jing (Ada Tai and Arlene Tai), to assist him in swapping fame for their help to return home.
Returning as a traveling salesman, Edward unwittingly aids Winslow in a bank robbery that secures Winslow's lucrative career on Wall Street, earning Edward a substantial commission, which he uses to fulfill his dream of buying a home with a white picket fence for Sandra. Meanwhile, in the present, Will investigates the veracity of his father's legendary life tales. Suspecting them as fabrications, he journeys to Spectre and meets an older Jenny, who reveals Edward’s pivotal role in rescuing the town from bankruptcy with the aid of his circus friends.
As Will reviews the past, he proposes the idea that Jenny might have been unfaithful to Sandra, yet she clarifies that while she harbored feelings for Edward, his loyalty to Sandra remained unwavering. Returning home, Will learns of his father’s stroke, during which he stays at the hospital to be by Edward’s side. There, the attending physician unveils the ordinary truth behind Will's birth, contrasting significantly with his father's embellished accounts. This experience leads Will to appreciate Edward's penchant for storytelling filled with wonder and fantasy.
When Edward regains consciousness but struggles to communicate, he implores Will to narrate a fictional conclusion to his life. With effort, Will weaves a tale of their daring escape from the hospital to a nearby lake, where a gathering of characters from Edward's colorful past awaits. They reach the water, and Edward transforms into a giant catfish, swimming away contentedly. Satisfied, Edward passes on, knowing that Will comprehends his father's deep-seated passion for storytelling.
At Edward’s funeral, Will and Joséphine are astounded to see all the characters from Edward's narratives, albeit in less fantastical forms than once described. Finally embracing his father's zest for life, Will decides to share Edward's stories with his own son, ensuring that the legacy of imagination continues to flow through generations.
