The novel begins with an incident near the end of the narrator’s father’s life, during a car trip. The father and son stop near a river, and the father puts his feet into the water and begins to remember something from his boyhood but stops before he tells his son the story. The narrator imagines his father as a timeless, mythical creature. Readers later learn that the narrator is Will and his father is Edward Bloom. 

Edward Bloom is born in Ashland, Alabama, during a drought. As his mother labors, a huge cloud appears, and it rains. Edward is an extraordinary child who can talk to animals and identify people by their footsteps. He knows everyone by name, and everyone loves him. According to the stories Edward tells, he builds a sixteen-foot snowman during a rare snowstorm, and his family sleeps in the trees. He has a growth spurt that puts him in bed for a year. He reads 10,000 books and remembers everything in them. Edward’s father is a farmer who grows a vine that reaches the clouds.  

The novel fast-forwards in time, with son Will recalling the time just before his father’s death. Edward does not like to sit still, so his serious illness is taking its toll on him. After Dr. Bennett tells them that nothing can be done, Will brings Edward a glass of water and they joke. Edward admits that he missed much of Will’s growing up, just like his own father did for him. Will tells him that having a son who loves him makes him great, which puts Edward at ease until he wants to tell another story. 

As a young man, Edward has a quiet charm which, along with his sense of humor, appeals to young women. He sees a young woman bathing in the Blue River and saves her from a snake. However, the snake turns into a stick when he throws it, and the mysterious girl disappears. Another time, Edward tames a ravenous giant named Karl who pillages Ashland. Young Edward visits Karl’s cave, wins his trust, and teaches the giant to farm. Another time, Ashland is so flooded that a lake covers it. Edward catches a giant catfish that pulls him underwater where he sees people from Ashland who have died in the flood.

At seventeen, Edward leaves home with nothing but his dreams. First, he passes through “the place that has no name”, a dark, damp town with strangely oppressed residents. When a man shows Edward around the town, he realizes that people get stuck here as they try to leave Ashland. The people try to get Edward to stay, but he moves on. A vicious black dog growls at Edward but then follows him out of town where he sees the mysterious Blue River girl for the second time. Edward is robbed and beaten. He reaches Ben Jimson’s Country Store where he meets the owner and his family. Edward stays there for a year and helps make the store more successful.

Edward goes to Auburn to college where his prowess includes running faster than anyone else. When his landlady has her glass eye stolen, Edward learns that a fraternity uses it in a hazing ritual. Edward returns the eye to the old lady who later appears at the barn and frightens the boys away. Edward sees a beautiful young woman kissing one of the boys from the fraternity. He asks the girl, Sandra Templeton, for a date, and she says yes, even though the fraternity boy, Don Price, has proposed to her. After three weeks, Sandra is in love with Edward, and he with her. Don follows them one night and Edward and Don fight, but Don loses. Edward asks Sandra to marry him, and she agrees.

Fast-forwarding again to the present, as Edward rests in his home while dying, he and Will talk about the possibility of heaven and hell. To Will’s frustration, every time they start to talk about something serious, Edward cracks a joke.

Edward meets his future in-laws, and Edward and Sandra move to Birmingham where he takes on three tasks: serving as a veterinary assistant, selling lingerie, and saving their neighborhood from a Helldog who threatens a young child. In time, Edward goes to war and serves on a naval ship that is torn open by a torpedo. After Edward jumps from the burning ship, the mysterious Blue River girl leads him to safety, along with crew members who follow.

The story returns to Edward’s decline while resting at home. Dr. Bennett and Sandra are frustrated by Edward, so Will goes in to talk to him. Will begs Edward to be serious, but Edward cannot. Edward knows exactly when he will die, and it’s not today. As a child, he had dreams that predicted the deaths of several family members. Edward tells yet another joke, which infuriates Will so much that he slams the door on his way out. 

The story moves back in time to Will’s birth. He is born on a day that Auburn beats Alabama in a football game. Edward thinks his job as a father is to fill up his son with wisdom and stories. While Will grows up, Edward travels all over the world, always returning home with outlandish stories. Edward saves Will’s life twice: Once by grabbing him from a ditch and another time by grabbing him from the air. Edward once dreams of his death. In the dream, crowds of people, each with a story of Edward’s generosity and power, wait outside his house. Edward waves to them from a window.  

As Will grows, Edward feels himself getting smaller. He travels more and more, staying away from home longer and longer. After Edward’s car breaks down in Specter, he buys the whole town, one parcel at a time. There, he discovers a beautiful young woman named Jenny Hill. Edward falls in love with her and moves her into a white house in town, but he’s gone so much that Jenny becomes bitter and strange. Weeds and then a swamp take over her house, so Edward must return fully to Sandra and Will.  

Soon, Edward learns that he is sick with cancer. He returns home, and his life begins to ebb, little by little. Edward swims every day, but the pool turns swampy and green. One day, Will thinks he sees Edward turn into a fish and calls an ambulance when Edward passes out in the water. Soon, Edward is in a hospital, hooked up to life support.

When Will goes into the hospital room to talk to his father, Edward still tells the same “stupid” jokes that he has always told. Will encourages him to be more serious and straightforward, but Edward’s behavior doesn’t change. The kind Dr. Bennett tends to Edward but finally admits that there is nothing more to do. Edward is near death when he asks Will to help him escape. After a serious conversation about fatherhood, Will drives his father to a river. When Will carries Edward to the water and releases him, Edward turns into a silver fish that swims away.