The story is told through a series of memories by Jacob Jankowski, a man living in a nursing home who can't remember if he is 90 or 93-years-old. In the nursing home, Jacob's life lacks excitement. He gets visited every Sunday by one of his five children and has good rapport with a kind nurse named Rosemary, but for the most part, Jacob's a tired old man whose life is highly regimented and scheduled. This all changes, however, when the circus parks right outside of the nursing home window, igniting Jacob's memories of his time working with the Benzini Brothers Most Spectacular Show on Earth.
As his memories begin, Jacob is a 23-year-old Polish American preparing for his final exams as a Cornell University veterinary student when he receives the devastating news that both of his parents have died in a car accident. Jacob's father was a veterinarian and Jacob had planned to join his practice in Norwich, New York. When Jacob learns that his parents' home has been mortgaged to pay for his tuition and that his father's practice will not become his own, he has an emotional breakdown and leaves his Ivy League school just short of graduation.
In the dark of night, Jacob jumps on a train, later learning it is a circus train belonging to the Benzini Brothers Most Spectacular Show on Earth. On the train Jacob is befriended by Camel, an old man and circus veteran, who persuades his companions not to throw Jacob off the train. Camel takes him under his wing and is able to find him odd menial jobs. When the owner of the circus, Alan J. Bunkel, "Uncle Al," learns of Jacob's training as a vet, he is hired to care for the circus animals. This leads Jacob to share quarters with a little person named Walter (who is known as Kinko to the circus) and his Jack Russell Terrier, Queenie. A few weeks later Jacob is summoned to examine Camel, who, after drinking "Jake" (adulterated Jamaican ginger extract) for many years, is unable to move his arms or legs. Fearing Camel will be "red-lighted" (thrown off a moving train as punishment or as severance from the circus to avoid paying wages),[3] Jacob hides him in his room.
The equestrian director, August Rosenthul, is a brutal man who abuses the animals in his care (such as the new elephant, Rosie) and the people around him, though he can also be charming and generous. Jacob develops a guarded relationship with August and his wife, Marlena, with whom Jacob eventually falls in love. August is suspicious of their relationship and physically assaults both Marlena and Jacob. Marlena subsequently leaves August and stays at a hotel while she is not performing. Uncle Al then informs Jacob that August has paranoid schizophrenia and utters a threat: reunite August and Marlena as a happily married couple or Walter and Camel get red-lighted.
A few days later, after discovering that August has tried to see Marlena, Jacob visits her in her hotel room. After he comforts her, they end up making love, and soon declare their love for each other. Marlena then returns to the circus to perform (and have secret meetings with Jacob), but refuses to allow August near her, which makes Uncle Al furious. Not long after her return to the circus, Marlena discovers that she is pregnant.
One night Jacob climbs up and jumps each train car, while the train is moving, to August's room, carrying a knife between his teeth intending to kill August. However, Jacob backs out, leaving the knife on August's pillow to send a message. When Jacob returns to his train car, he finds that no one is there, except for Queenie. He then realizes that Walter and Camel were red-lighted and that he was also supposed to have been too.
As the story climaxes, several circus workers who were red-lighted come back and release the animals, causing a stampede during the performance.
In the ensuing panic, Rosie (the elephant that August abused) takes a stake and drives it into August's head. August's body is then trampled in the stampede. During the ensuing melee Jacob was the only person who witnessed what truly happened to August. As a result of this incident, the Benzini Brothers circus is shut down. Soon after, Uncle Al's corpse is found with a makeshift garrote around his neck. Marlena and Jacob leave, taking with them a number of the circus animals including Rosie, Queenie, and Marlena's horses. Jacob and Marlena begin their life together by joining the Ringling Bros. Circus. Later, Jacob becomes the chief veterinarian at the Brookfield Zoo in Chicago, where they settled.
The story then comes back to Jacob in the nursing home. Jacob is waiting for one of his children to take him to the circus. It is revealed that Jacob and Marlena married and had five children, spending the first seven years with Ringling before Jacob got a job as a vet for the Brookfield Zoo. Marlena is revealed to have died a few years before Jacob was put into the nursing home. After finding out no one is coming for him, Jacob makes his way to the circus next to the nursing home on his own. He meets the manager, Charlie, and, after the performance, Jacob begs to be allowed to stay with the circus, selling tickets. Charlie agrees, and Jacob believes that he has finally come home.
