Plot
Sarah and her friend Linda are going through a box of her late mother's belongings when they find a Polaroid SX-70 camera. Sarah takes a photo in lingerie on the Polaroid camera for her boyfriend, feeling uneasy. Linda leaves soon after. When she takes a look at the Polaroid, there is a creepy shadow behind her in the photo of her. She gets killed on the same night by an entity.
Shy high school student Bird Fitcher is given an old Polaroid camera by her co-worker Tyler, who got it from a garage sale. The camera has the initials "RJS" carved into it. Bird snaps a picture of Tyler but later notices an odd smudge-like figure on his photo.
Bird attends a costume party with her best friend Kasey and meets her other friends Mina, Mina's boyfriend Devin, Avery, and Bird's high school crush Connor. She uses her Polaroid camera to take the group's picture and Avery later snaps a selfie with it. Meanwhile, Tyler is killed by the entity, and Sheriff Pembroke informs Bird. At home, Bird sees Tyler's photo free from the shadow, which has mysteriously transferred to Avery's photo.
Avery is killed when the entity snaps her neck. When Bird learns about this, she tries to destroy the camera and attempts to warn her friends. Devin attempts to burn the group photo, but when the flames reach Mina in the photo, her arm spontaneously combusts and the flames cannot be extinguished. Kasey's fingers are slightly singed before Bird stomps out the fire and the photograph restores itself. Mina is taken to the hospital to undergo surgery for her arm; Devin and Kasey stay with her while Bird and Connor leave to learn more about the camera. While in the antique store, Bird is attacked by the entity, which behaves like a photograph: following the same rules as photographic development (i.e. it is sensitive to heat). She questions why she was chased too and notices that her reflection is in the photo's background.
Mina is killed at the hospital by the entity. Bird and Connor research and discover that the camera was owned by a photography teacher Roland Joseph Sable from their school years ago. He was accused of torturing four students and killing three of them while taking maniacal photographs. One of the captives escaped and Roland was killed by police. Devin confronts Bird at the diner and accuses her of being responsible for what happened to Mina. He attempts to take a picture of her as a threat. With Connor and Devin both fighting for the camera, Devin is accidentally snapped by the camera and the shadow transfers to his photo. Devin lunges at Bird, Kasey saves Bird by stabbing Devin's photo with a pencil, injuring him in real life. Devin, upset from being stabbed, becomes aggressive and accidentally slaps Sheriff Pembroke. Devin is detained and is later killed in his cell when Roland manifests and attacks him.
Connor, Kasey, and Bird learn Roland's wife is alive and visit her. They meet an elderly lady named Lena Sable, who explains that the camera actually belonged to her daughter Rebecca Jane Sable. Lena explains that Rebecca was "slow," and when gifted with the camera she became very attached to it. As a result, Rebecca was bullied by four classmates, who took the camera and used it to take inappropriate photos of her. She killed herself out of shame, causing her father Roland to abduct and kill her bullies in a fit of rage. Now even in death, Roland roams, looking for the last bully who escaped to kill him. Lena shows the two a picture of the survivor and they search the yearbooks. Bird finds out that the survivor was Sheriff Pembroke. In an attempt to stop the entity from killing them, Connor takes a picture of Pembroke, who reveals that Roland in truth often sexually assaulted Rebecca; Lena's version of the events was merely just to cover her husband's evil deeds. The four students, including him, were Rebecca's friends trying to warn her of her father's actions upon finding her nude pictures in his possession. Fearing the public would find out, Roland abducted them, prompting Rebecca to kill herself out of misplaced guilt.
Shortly after, Roland manifests and ambushes the group, killing Pembroke, and injures Kasey. Connor gets separated; the girls find safety in the school's showers, with Bird turning on the hot water to create heat to ward off Roland. Bird reunites with Connor, and she has an idea that involves retrieving the camera and going somewhere where Roland can "fully develop". Roland manifests and drags Connor away, but Bird takes a picture of herself, prompting him to chase her instead. She leads him into the school's dark room, where he is able to fully develop, but the entity ambushes her. As Roland prepares to kill her, she manages to discreetly retrieve the camera and take a picture of him. Bird immediately crushes the photograph. Roland survives however, and she burns the photograph, disintegrating Roland for good. She later reunites with her friends, and ultimately throws the camera into a river.
