In 2006, a spaceship crashes in Brightburn, Kansas. Tori and Kyle Breyer, who are unable to conceive a child, look inside to find an infant. The couple adopts the child and names him Brandon. They hide the spaceship in their barn to conceal the truth from him.

In 2018, the ship begins transmitting an alien message, causing Brandon to sleepwalk to the barn. He tries to open the cellar, but Tori intervenes. Brandon begins to exhibit superhuman powers.

One day during a trust exercise in PE, Brandon falls toward a girl in his class named Caitlyn; she lets him fall and accuses him of being a pervert, having previously seen him in her room at night. Caitlyn is forced to help Brandon up, and Brandon, frustrated by her actions, crushes her hand. That night, Brandon sleepwalks once again to the ship and breaks into the barn where it is hidden. Tori follows and sees him levitating, chanting the ship's message: "Take the world." Tori reveals the truth of his origin, and Brandon goes on a rampage, killing Erica Connor, Caitlyn's mother, after Erica expressed displeasure towards him because he broke Caitlyn's hand. Police find a series of runic drawn on a window while investigating Erica's disappearance.

The next day, Brandon kills his uncle Noah by lifting and crashing his vehicle. The following morning, Tori and Kyle inform Brandon of Noah's death, but Brandon shows no emotion or empathy, angering them both. Kyle accuses Brandon of murder and grabs him, and Brandon retaliates by violently shoving him. Kyle finds Brandon's blood-stained shirt and shows it to Tori, but she refuses to believe it.

Kyle takes Brandon on a father-son hunting trip in the woods. Kyle attempts to shoot and kill Brandon with his hunting rifle, but the execution fails when the bullet bounces off the back of Brandon's head. Realizing what Kyle has just tried to do, Brandon chases him and kills him with heat vision. A sheriff arrives at the Breyers' and asks to see Brandon. Tori tells the sheriff that Kyle and Brandon aren't home, so he shows Tori the symbol found at the scenes of Erica's and Noah's deaths. Tori finds Brandon's notebook with drawings of his murders and his message to "take the world" and begins to believe Kyle. She tries calling Kyle, but Brandon answers and implies he is now coming for Tori.

Brandon returns and begins destroying the house, easily killing all cops who come to the rescue. Remembering that the ship can injure Brandon, Tori runs to the barn and discovers Erica's eviscerated body. As Brandon pursues her, Tori tries to tell him about how much she loves him. Tori then tries to stab him with a piece of the ship, which Brandon sees coming and avoids. In retaliation, Brandon flies Tori miles into the sky above the clouds and drops her to her death, just as an airplane approaches. The next day, the airplane is revealed to have mysteriously crashed into the farmhouse, with the news reporting that everyone on board was killed and that Brandon was the only survivor.

During the credits, Brandon begins his worldwide attacks, which news reports cover. Brandon is also dubbed "Brightburn" by the media. A conspiracy theorist named Big T discusses the Brightburn incident and the existence of other super-powered beings, pleading with humanity to take action.

https://en.wikipedia.org/wiki/Brightburn
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