Bridge to Terabithia is a children's novel that tells the story of young neighbors Jesse Aarons and Leslie Burke, two lonely children who become close friends. While playing in the woods they form the imaginary kingdom of Terabithia, a place where they can escape from the troubles of their everyday lives. When Leslie unexpectedly dies, Jesse must learn how to cope with her loss in this story which touches on themes of friendship, identity, and the magic of childhood.
The book chronicles the life of an artistic young boy named Jesse Aarons and the burdens and hardships of his home life, such as his duties on his family's farm and the constant agitations and annoyances of his four sisters. Jess has straw-colored hair and long legs. After having trained all summer to become his classroom's fastest runner, he is infuriated when this position is claimed by an intelligent and fast newcomer named Leslie Burke, whom he strongly dislikes. After further negative experiences with classroom tormentors or rivals, including Gary Fulcher, Jess eagerly anticipates the arrival of music class due to his strong infatuation for its beautiful young teacher, Miss Edmunds.
However, on the day music class begins, he discovers a fondness for the eccentric and ostracized Leslie, and they develop a friendship. While swinging together over a creek on a sunny day, Jess and Leslie decide to design an imaginary sanctuary from the burdens and pains of everyday life. The pair reign as monarchs, calling their domain Terabithia and constructing a small refuge in which their imaginary escapades take place.
At school, the pair are challenged by an older bully named Janice Avery, whom they immensely detest. After Janice steals a package of Twinkies from Jesse's younger sister May Belle's lunch, they forge a romantic letter under the disguise of Willard Hughes, the object of Janice's infatuation, in conspiracy against her. After the plan's success exposes Janice to public mortification, the triumphant Jesse and Leslie indulge in their victory; however, after encountering a sobbing Janice in the girls' bathroom one day and learning of the abuse to which she is subjected, Leslie develops sympathy for and a friendship with the misunderstood bully. In the meantime, her bond with Jesse also increases powerfully, and they continue to indulge in the pleasures derived from Terabithia, adopting a puppy named Prince Terrien, abbreviated to P.T.
On being invited to a trip to an art museum with Miss Edmunds, Jesse accepts the offer without notifying Leslie or his parents beforehand. He enjoys the day with his teacher, but upon returning home is horrified to learn that while he was away, Leslie attempted to visit Terabithia on her own and died of drowning when the rope swing broke. A shocked Jesse, incapable of absorbing or accepting the impact or horror of Leslie's sudden death, denies his grief and even his friend's existence, while internally terrified that Leslie may be sentenced to eternal damnation due to her doubts regarding religion. After he miserably accepts the inevitability of her death, Jess is saddened even further by the grief exhibited by her mourning family, who have decided to return to their previous home in Pennsylvania. They grant Jess some of the lumber they are leaving behind.
He decides to pay tribute to his deceased friend by crafting a funeral wreath by bending a pine bough into a circle, but before that he discovers a terrified May Belle by the creek, after she has attempted to use a fallen tree to get to Terabithia. After assisting her, he uses the lumber he took from the Burkes' home to build a truly safe bridge. He chooses to fill the void left by Leslie's passing by making May Belle the princess of Terabithia and presumably the queen in future, permitting her to share his sanctuary from then onward. Then, Jess tells May Belle to keep the "mind wide open" and all of the inhabitants of Terabithia welcome their new princess.