Plot
A spaceship crashes in a forest in Brightburn, Kansas. Tori and Kyle Breyer, a couple struggling with infertility, witness the explosion from their house and investigate the crash site. They find the spaceship with a baby inside, whom they adopt and name Brandon.
On Brandon's 12th birthday, he discovers that he has super-strength and flight abilities. In middle school, Brandon is an academically exceptional student, despite being introverted and frequently bullied. Brandon begins to show interest towards his classmate Caitlyn Connor, sneaking into her room at night and scaring her.
One day, during a trust exercise in a Physical Education class, Caitlyn refuses to catch Brandon, and makes him fall to the ground, calling him a pervert. Humiliated by her accusation, Brandon crushes her hand, and is suspended from school after being accosted by Caitlyn's mother, Erika, who wants him arrested.
At night, the spaceship emits an otherworldly language that attracts Brandon to the barn. Tori follows, and sees him levitating, chanting the ship's alien message, before falling and accidentally cutting his hand on the wrecked ship. She reveals the truth of his origin, causing Brandon to declare his hatred towards his adoptive parents and storm out of the house. Brandon deciphers the spaceship's message ("Take the world"), causing his evil identity to take over. As an act of revenge, Brandon uses his powers to torment and kill Erika at a diner.
Police discover a symbol drawn on all diner windows, made visible when the sheriff breathes on one of them while investigating Erika's disappearance. It is the same symbol Brandon is seen drawing in his notebook. Brandon visits his aunt's house to convince her to keep his incident at school a secret, but she refuses. Feeling rejected, Brandon begins to stalk her around the house but gets caught by his uncle, Noah. After Noah threatens to tell his father about his behavior, Brandon toys with him before killing him by telekinetically lifting and dropping his truck as he tries to escape. Brandon reaches into the wreckage and dips his finger in his uncle's blood to draw his notebook symbol on the pavement.
Tori and Kyle inform Brandon of Noah's death, which the police believe was an accident. Brandon attempts to cover up his action by dismissing his involvement. Suspecting him to be the culprit, Kyle finds Brandon's blood-stained shirt, and shows it to Tori, who refuses to believe Brandon is responsible. Kyle lures Brandon on a father–son hunting trip in the woods. He attempts to shoot Brandon with his hunting rifle, but the bullet bounces off the back of his head. Brandon retaliates and kills Kyle with heat vision.
The sheriff arrives at the Breyers' residence, showing Tori the symbol found at the scenes of Erika's and Noah's deaths, suggesting they are connected. Tori finds Brandon's notebook with drawings of his murders and the message, "Take the world." She calls Kyle, but Brandon answers, saying he is coming for her.
Brandon returns and begins destroying the house. Tori calls the police, but Brandon swiftly kills the officers before backup can arrive. Remembering that the ship's hull can harm him, Tori runs to the barn and discovers Erika's eviscerated body near the ship. Brandon pursues her into the barn. When he finds her, Tori tries to reassure the good side of Brandon. Using the distraction to get close, she attempts to stab him with a metal piece of the ship, but Brandon anticipates the attack and catches her arm. Heartbroken and enraged by her betrayal, he takes her high up to the stratosphere and drops her to her death. After watching her fall, he notices an oncoming airplane.
The following morning, the airplane is revealed to have crashed into the farmhouse, destroying evidence of the murders from the previous night. Brandon's symbol is seen painted on a piece of the plane wreckage as rescue workers attend to him. In the credits, Brandon is seen in news reports over the locations of various disasters as an online conspiracy theorist points out the existence of other superpowered beings and urges the public to take action before it is too late.
