Plot
Finn (Matt O'Leary) is a painter with a creative block, who lives together with his girlfriend Callie (Danielle Panabaker) and his best friend Jasper (George Finn) in an apartment complex where Finn works as a manager. Because elderly tenant Mr. Bezzerides (informally called "Mr. B" by the protagonists) has not paid his rent in two months, Callie checks on him, and discovers a strange machine in his apartment that takes Polaroid photos of their living room's picture window—apparently 24 hours in the future, always at 8 pm, although Mr. B's photo display includes daytime photos and is missing some photos. The friends check Mr. B's storage unit and find his inexplicably charred corpse; he has apparently been dead for a week. Gambling addict Jasper pushes to use the machine to win bets but loses, and the next day's photo confirms they will do just that. It also shows that Finn has finally created a new painting; copying the work in the photo gets him past his block. Based on what happened to Mr. B and notes in his journal, they theorize that they have to make sure the events in the photos—whatever they may be—have to occur, or their timeline will stop, and they will therefore cease to be.
Several days go by. The friends cover up Mr. B's disappearance, including lying to the complex security guard, Big Joe, claiming the old man is in the hospital. After a week they get a disturbing photo: Callie kissing Jasper, while Finn paints in the background. Feeling that they have to do what's in the photos, they pose at 8pm the following night. But the actual kiss goes on too long while Finn paints, and he gets angry and jealous.
The next photo shows Jasper's violent bookie Ivan at the apartment. Not knowing why he would be there, Jasper calls him the next morning, saying he won't be making any bets that day. The call raises Ivan's suspicions and he visits Jasper that night, learning of the machine. Ivan forces the friends to now pose for the photos with many more event results for Ivan to make bets on. Finn and Jasper's friendship is strained by these events, as Ivan will be keeping each night's photo, preventing Finn from seeing his painting. Jasper manages to get a cellphone picture of the next photo before giving it to Ivan's goon, Marcus. This photo shows a hastily made skull and crossbones on the canvas, which Jasper believes is a warning to themselves, so he hides weapons (a kitchen knife, golf club, and hammer) near the couch.
The next evening, Finn runs into Big Joe at the gate, who has just gotten a job as a police officer. Marcus sees their meeting and calls Ivan, who does not believe their story about Big Joe. Ivan threatens all of them, but Jasper convinces him that tonight's new photo is of Ivan's death at Marcus' hands. While Ivan is retrieving the photo, Jasper stabs Marcus, then clubs Ivan to death on his return. They hide the bodies in Mr. B's storage unit. Finn and Callie fight, so Finn sleeps on the couch. Later that night, they are visited by Mr. B's colleague, Dr. Heidecker, who is looking for Mr. B. Finn and Jasper can't keep their stories straight about Mr. B, so Dr. Heidecker levels a gun at them and forces them to confess. Mr. B had mailed Heidecker a photo that covers the next night, but taken before his death, meaning that the machine could be set to take photos more than 24 hours in advance. The photo shows blood on the window, Mr. B's hat on the friends' couch (Jasper has taken to wearing the dead man's hat), and a picture of a green coil that resembles the broken device on the ground next to Mr. B's corpse. Dr. Heidecker theorizes that "time" did not kill Mr. B for trying to change the future - he knocked over a coil in his storage unit and the released gas killed him. As she does not know how to adjust the settings of the machine, Jasper shoots Heidecker dead using Ivan's gun.
The next night's photo shows Callie and Jasper having sex in the window with Finn unconscious on the couch. Finn talks with Jasper to try to devise means to prevent events, but Jasper knocks him out and locks him in Mr. B's storage unit — he does not believe Dr. Heidecker's theory and intends to prevent a paradox, making sure the photo happens no matter what. Trying to find a way out of the locked storage unit, Finn searches Heidecker's purse and finds the photo with the blood, Mr B's hat, and the painting of the coil; he realizes that he must be able to escape in order to paint the coil the next day so that Mr. B could take a picture of it in the first place. Finding Mr. B's keys he does so; he escapes, goes to the machine, and calls Jasper, threatening to destroy it if Jasper does not stop. A fight ensues, culminating with Callie smashing Jasper's head in.
When making the painting to match Heidecker's photo, Finn realizes a discrepancy. He discovers that the camera also takes a photo at 8 am, a truth which Callie kept to herself. Callie reveals that she has been using the morning photo to send herself messages to manipulate events and rekindle her relationship with Finn; the sex photo is one of those missing from Mr. B's wall, from a drunken night a month ago (the other missing photos are ones of Callie and Jasper being affectionate, which she took down from the wall when she first discovered the machine). Finn rejects Callie and goes to destroy the machine, so she shoots him, creating the blood splatter on the window from Heidecker's photo.
Callie writes a warning message on a piece of paper and sticks it to the window, believing that when her past self sees it via the photo, it will prevent the events of the previous 24 hours from happening. While she is doing so, Big Joe stops by, discovers the murdered Jasper and Finn, and arrests her. As Callie is led away by Joe - confident that the timeline will reset - the note she left falls off the window; it is revealed that the timeline is, in fact, immutable, and Callie was mistaken in thinking she had any control over it. The camera takes the photo that Mr. B had mailed to Heidecker before he died, and generates another photo, which is left unrevealed.
