A mysterious, wavering light that resembles a flame flickers in the darkness. Mrs. O’Brien (Jessica Chastain) recalls a lesson taught to her that people must choose to either follow the path of grace or the path of nature. In the mid 1960s, she receives a telegram informing her of her son’s death at age 19. Mr. O’Brien (Brad Pitt) is notified by telephone. The family is thrown into turmoil. In the present day, Jack O’Brien (Sean Penn) is adrift in his modern life as an architect. When he sees a tree being planted in front of a building, he begins to reminisce about his life as young teenager during the 1950s.
The universe is formed. As the galaxies expand and planets are formed, voices ask various existential questions. On the newly formed Earth, volcanoes erupt and microbes begin to form. An Elasmosaurus, a large wound in its side, gazes out to sea. In a forest, a youngParasaurolophus is wary of predators. Later on a riverbank, the Parasaurolophus lies wounded. An Ornithomimus emerges and examines the wounded dinosaur. The Ornithomimus places its foot on the Parasaurolophus’ neck, preparing for the kill, but then reconsiders after watching it struggle. The predator wanders off. An asteroid impacts the earth.
In a sprawling neighborhood in Waco, Texas, live the O’Briens. The young couple are enthralled by baby Jack and, later, his two brothers. When Jack (Hunter McCracken) reaches adolescence, he is faced with the conflict of accepting the way of grace or nature, as embodied by each of his parents. Mrs. O’Brien (grace) is gentle, nurturing, and authoritative, presenting the world to her children as a place of wonder. Mr. O’Brien (nature) is strict, authoritarian, and easily loses his temper as he struggles to reconcile his love for his sons with wanting to prepare them for a world he sees as corrupt and exploitative. He laments his decision to become an engineer rather than pursue his passion of becoming a musician, and now pursues dreams of wealth by filing patents for various inventions.
One summer, Mr. O’Brien takes a trip around the world in an effort to commercialize his inventions. While he is away, the boys enjoy unfettered access to their mother, and Jack experiences the first twinges of rebelliousness. Goaded by other boys his age, Jack commits acts of vandalism and animal abuse. He later trespasses into a neighbor’s house and steals her underwear. Jack is confused by his experiments with violence and experiences guilt, throwing the stolen underwear into a river to rid himself of it. Mr. O’Brien returns home, having failed to sell any of his inventions. Shortly thereafter his plant closes and he is given the option of staying with the company and relocating to work a stable yet unfulfilling job, or be terminated. Mr. O’Brien agrees to the transfer and he and his family pack up to move. Mr. O’Brien laments the course his life has taken, questioning whether he has been a good enough person. He reconciles with Jack, asking forgiveness for his harsh treatment of him.
Far in the future, the planet Earth is destroyed, first burnt to cinders by the sun when it has turned into a red giant and then left alone as a desolate, lifeless frozen place still orbiting around the sun, which by that time has turned into a feeble white dwarf.
In the present, adult Jack leaves work. Riding the elevator down he experiences a vision of walking on rocky terrain. He tentatively walks through a wooden door frame which is erected on the rocks. On a sandbar, Jack is reunited with his family and all the people who populate his memory. His father is happy to see him. His mother is overjoyed when Jack’s memory resurrects his dead brother. She thanks Jack, kissing his arm twice. Jack’s vision ends and he leaves his building smiling.
The mysterious, wavering light continues to flicker in the darkness.