Ben Cash, his wife Leslie and their six children live in the Washington wilderness. Ben and Leslie are former anarchist activists disillusioned with capitalism and American life, and chose to instill survivalist skills, left-wing politics, and philosophy in their children - educating them to think critically, training them to be self-reliant, physically fit and athletic, guiding them without technology, demonstrating the beauty of coexisting with nature and celebrating "Noam Chomsky Day" instead of Christmas.
Leslie is hospitalized for bipolar disorder and eventually dies by suicide. Ben learns that Leslie's father Jack plans to hold a traditional funeral and burial, even though Leslie wished to be cremated. They argue over the phone and Jack threatens to have Ben arrested if he attends the funeral. He initially decides not to go and prevents his children from doing so, but then changes his mind, leading his children on a road trip into life outside the wilderness.
The family briefly stays at his sister Harper's house. She and her husband try to convince Ben that his children should attend school to receive a traditional education; Ben argues that his children are better educated than Harper's own children. Ben arrives at Leslie's funeral with his children and reads her will, which instructs her family to cremate her and flush her ashes down the toilet. In response, Jack has Ben forcibly removed.
Ben's children also start doubting their father and his parenting skills. His son Rellian accuses Ben of failing to treat Leslie's mental health. His son Bodevan accuses his father of failing to equip them for the real world by setting them up for a rude awakening when they grow up and shows him college acceptance letters from Ivy League schools for which Leslie had helped him apply. Rellian wants to live with his grandparents, who want to take custody of them. When Vespyr tries to climb into a window to "free" Rellian from his grandparents, she falls from the roof and narrowly avoids breaking her neck. Ben, shocked and guilty, allows Jack to take his children. Although they have bonded with their grandparents, the children decide to follow Ben again when he departs.
The children honour Leslie's wish and convince Ben to help them, exhuming her corpse, burning it in a self-made pyre and flushing her ashes down an airport toilet. Bodevan then leaves the family to travel through Namibia, while the rest settle on a farm. The final scene is the family around the kitchen table with their father, waiting for the school bus to arrive.