T.S. Spivet, portrayed by Kyle Catlett, is a bright young boy living in the isolation of a Montana ranch alongside his moody older sister, Niamh Wilson, his pretentious entomologist mother, Helena Bonham Carter, and his emotionally distant wannabe cowboy father, Callum Keith Rennie. Struggling with loneliness and often feeling belittled by those around him— including his envious schoolteacher— T.S. finds solace in creating amateur inventions and wandering the ranch with his loyal dog, Tapioca.
Haunted by the loss of his older brother Layton, played by Jakob Davies, T.S. grapples with a haunting past that deeply scars his family. He recalls a tragic accident from their childhood when a game with their father's gun led to Layton’s untimely death, a moment that T.S. believes he caused. Although this traumatic event isn't depicted on-screen, its impact lingers heavily over the family dynamic and T.S.'s psyche.
When T.S. learns that he has been awarded the Baird Award by the Smithsonian Institute for his creation of a perpetual motion machine, he makes the bold decision to escape his confining life. Skeptical about assuming his identity over the phone, Ms. Jibsen, the museum director played by Judy Davis, mistakenly believes T.S. is the son of the award's true winner. Despite his initial hesitation, T.S. sees this opportunity as a means to find his place in the world and sets off on an adventurous journey across the country.
Before departing, T.S. takes a moment to say goodbye to his brother's old room, a poignant shrine filled with forgotten toys and memories. As he sneaks away, neither his sister nor father acknowledges his departure, lost in their own lives.
T.S.'s adventure begins on a train, where he imagines conversations with Layton, momentarily losing himself in nostalgic memories amidst the sounds of the train. After a close call with a guard, he cleverly hides in an auction show camper, even mimicking a lifelike cardboard family to blend in. On his nightly escapades for food, he encounters a whimsical hobo named "Two Clouds," portrayed by Dominique Pinon, who shares a story about the journey of a sparrow and a pine tree, further inspiring T.S. to consider the paths people take in life.
A day later, as T.S. walks along the train tracks with his backpack, he's pursued by a mean-spirited policeman, played by Harry Standjofski, leading him to a daring climb atop a bridge. After a tense moment, T.S. narrowly escapes and soon finds a ride with a friendly trucker named Rick, played by Julian Richings, whose own history with post-traumatic stress disorder adds depth to their conversation. Rick encourages T.S. to seek medical attention for an injury he suffered earlier, demonstrating compassion amidst their unforeseen friendship.
Upon arriving in Washington, T.S. meets with Ms. Jibsen at the Smithsonian, where she remains skeptical of his accomplishments. In a moment of vulnerability, T.S. claims to be an orphan, fearing the confrontations that might arise from his family discovering his whereabouts. Despite Ms. Jibsen's overwhelming desire to take him under her wing, T.S. feels isolated even in a crowded room as he prepares to accept his award.
During the award ceremony, T.S. delivers an emotional speech, revealing to the audience the heartbreaking truth about Layton's fate, moving them to tears as he laments: > "Nobody ever even talks about Layton anymore, as if my brother never even existed." Little does he know, his mother has traveled all the way to witness her son’s moment.
The emotional reunion quickly escalates tensions, as Ms. Jibsen realizes she's lost control over T.S. to his family. Amidst a chaotic scene, his mother passionately embraces him, and T.S.'s father instinctively defends his son from harassment, showcasing the protective instincts of a caring parent.
Returning home brings new revelations, and T.S. shares in an epilogue that his family has welcomed a new baby. Utilizing his inventive spirit, he creates an even better perpetual motion machine, ingeniously using it to rock his infant sibling's cradle on the porch, indicating a new chapter of hope and continuity for the family.
