Josh Whitney Jacob Tierney and his younger brother Sam Noah Fleiss are traveling from their mother’s house in the San Fernando Valley region of California to stay with their father Thom Stephen Tobolowsky and his new family in Orlando, Florida. Their mother Caroline Whitney Joan Allen is engaged and set to remarry a man Josh doesn’t particularly trust, a situation that sparks tension and a desire for retaliation in Josh.
Josh, feeling like the black sheep of Thom’s blended clan, hatches a dangerous plan that centers on Sam. He subtly convinces Sam that he is a genetically designed child warrior, an acronymized hero named S.A.M.(“Strategically Altered Mutant”). What starts as a family rift fueled by lies spirals as Josh’s fabrications compound and Sam, lured by the idea of power and belonging, begins to believe the fantasy that Josh has spun around him.
Thom, trying to keep the pieces of his life together, orders the boys to fly back to California to retrieve their belongings because their mother and her fiancé plan to move to Europe for a year and the boys will move in with Thom. The family split becomes a road map of miscommunications and escape routes, with each decision pulling the brothers further from the truth.
A fierce thunderstorm grounds the flight in Dallas, forcing Josh and Sam to spend a night in a hotel. Frustrated with his family’s instability, Josh seizes the moment to cut Sam loose, and while the hotel staff keep watch, he crashes a high-school reunion and lies that his mother was a graduate. It’s at this reunion that Josh crosses paths with Derek Baxter [Chris Penn], a drunken man who claims to have been involved with the woman whose pin he stole. Before Josh can correct the record, Sam arrives and sticks close, and the uneasy trio heads off together.
Derek drives them to a random house, where Josh attempts to call the police by breaking in. Derek spots a photograph of the real family and confronts the brothers about their deception. In a tense confrontation, Sam strikes Derek with a billiard ball while Josh bludgeons him with a pool cue, knocking him unconscious. Fearing the consequences of their actions, the boys flee and steal Derek’s rental car, setting off on a cross‑country ride across the Western United States.
Along the way, they encounter Allison Martha Plimpton, a runaway from Hannibal, Missouri, whom they mistakenly believe to be “The Liberty Maid” from Josh’s tall tales. The trio finds themselves in a precarious alliance as they dodge authorities and inch toward the edge of the map. Allison’s presence adds a new dynamic to the escape, and she travels with them as they drift through small towns and big highways, their flights of fancy growing with every mile.
During a late-night stop at a motel, Sam seizes control of the stolen car and abandons it on the roadside. Josh locates the broken-down vehicle and, with little choice, hops a bus. He later spots Sam clinging to the back of a tractor-trailer unit, a sight that drives him to abandon the bus and pursue reuniting with his brother at the next checkpoint—bordering on a legal crossing into Canada, the brothers slip through a fence and into a new country.
In Canada, Josh tries several attempts to come clean about his fabrications, but the urge to protect the lie keeps him from confessing. He eventually stops the pursuit and sends Sam back toward Orlando by plane. Josh, feeling unwanted and adrift, decides to stay in the unfamiliar country, while Sam eventually reaches Orlando and reports Josh’s whereabouts to Thom.
Thom travels to Dallas and speaks with the local police, who confirm Derek was not killed by Josh but knocked unconscious from the earlier confrontation. Upon returning to Orlando, Sam greets Josh with a twist of his own: using a computer file trick to reveal a hidden truth about him, Sam turns the tables and exposes the tangled web of lies that started the chaos. The resolution rests on the fragile bonds of family, trust, and the consequences of deception that stretch across state lines and into the hearts of two brothers.
