NOTE: This spoiler was submitted by Emilio.
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 the elderly tenant, "Mr. B", across the way has not paid his rent in two months, Callie goes to check 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. 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, as he usually 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 Polaroid gets him past his block. Based on what happened to Mr. B and notes in his journal, they realize 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. The actual kiss goes on too long while Finn paints, and he gets angry and jealous. Jasper's violent bookie Ivan learns of the machine, and 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. Even so, Jasper gets a cellphone picture of the next Polaroid 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.
The next evening, Finn runs into Big Joe at the gate, as he has just gotten a job as a police officer. Marcus sees their meeting and calls Ivan, who doesn't believe their story about Big Joe just dropping off his keys. Ivan threatens all of them, but Jasper convinces him that tonight's new photo is of Ivan's death. 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 levels a gun at Finn and Jasper and forces them to reveal events. Mr. B had mailed Heidecker a photo that covers the next night, but taken before his death, showing blood on the window and Mr. B's hat on the friends' couch (Jasper has taken to wearing the dead man's hat). As she doesn't 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. Finn talks to Jasper, trying to figure out a way to prevent events, but Jasper knocks him out and locks him in Mr. B's storage – he's going to prevent a paradox and make sure the photo happens, no matter what. Finn escapes and threatens to destroy the machine if Jasper doesn't stop. A fight ensues which ends with Callie smashing Jasper's head in. Callie tells Finn that she is going to get some ice for his head. Finn starts to paint the picture in from Heidecker. When making the painting to match Heidecker's photo, Finn realizes a discrepancy. He goes to Callie and sees her in the kitchen messing with something in a drawer. He tells her that he thought she was going to get some ice. She awkwardly says she was and tries to make it look like she was. She takes Finn to the bedroom where he lies down with the bag of ice to his head. Afterwards, she hurriedly leaves the room and closes the bedroom door behind her He lies down for a few seconds and then gets up. He slowly opens the bedroom door and heads out. He goes to the living room where he sees Callie in front of the window with two pieces of papers with some phrases written on them that Callie has taped to the window. There is suddenly a flash from the camera. He asks Callie about the camera flash. She tells Finn that she can explain. Callie takes the pieces of paper off the window and reads them. One of the papers reads "SWAP PHOTO WITH CHARADE NIGHT" and the other reads "KILL JASPER TO SAVE FINN". Finn drops the papers on the floor and goes to the kitchen. He opens the drawer that Callie was messing with earlier and some stuff falls out. Callie tries to get Finn to go to the living room so that they can talk, but Finn tells her to tell him the truth.
Callie tells him the truth. She says that when she went to Mr. B's to tell him that he was behind on his rent, she knocked on his door. When he didn't answer, she went inside his apartment. Inside, she found the machine. She says that a photo was sticking out of the machine. The photo was of her. The photo showed her with her finger over her mouth, telling her to be quiet. Beside her are two pieces of paper. On them are written "KNOCK COAT RACK OVER" and "HIDE LAST WEEK'S DAYTIME PHOTOS". She tells him that the camera also takes a photo at 8 am, which she has been concealing from them the entire time. 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. She says that when Finn saw her in the kitchen, she was hiding the photo. She tells him that the sex photo was taken because she got drunk.
She tries to reason with Finn, telling him that the photo was like her wanting to be caught, so that Finn would "wake up" and realize what he had. He says that he can't believe that she would do this. He tells her that she had every opportunity to prevent it and to warn him. He asks her why she didn't. She tells him that she was only doing what the photos told her to do. She was getting pulled along like they all were. She tells him that everything happened for a reason. She grabs a photo, which shows her and a piece of paper reading "KISS JASPER TOO LONG", which Callie says made Finn jealous for the first time in ages. She tells Finn that he's been increasingly distant, but lately has become more close to her since the discovery of the machine.
She shows him another photo. This one has her and another piece of paper which reads "GO WITH FINN TO CAR". She tells him that she got to feel his kiss again, as a result of her message. A third photo has the message "POSE FOR FINN". This was so that Finn could paint her and that he would realize what he had. A fourth photo has the message: "BUY MODELING BOOK". Callie says that slowly they were coming back together as a couple. The fifth photo says "DON'T FORGIVE FINN". Callie tells Finn that after everything that was happening, he was still picking the machine and his work over her. She says that she had to do something that was going to bring him back to his senses, which led to the current photo. She tells Finn that she saw him fight for her more than she has ever seen him fight for anything. She says that in the end, everything worked out
He seemingly agrees with her, but ends up rejecting Callie. He gets up and goes to destroy the living room. Callie comes in and asks him what he's going to do. He says that he's going to destroy the machine. Callie tries to talk him out of it, even saying that she can leave a note for the night photo warning her to hide the photos so that Finn does not catch her in the morning. Finn looks at her disapprovingly and begins to head over to the machine to destroy it. As a result, Callie picks up the gun and points it at Finn. She tells him that if he does, she will shoot him. As he does, Callie shoots him. This, in turn, creates the blood splatter on the window from Heidecker's photo. When Callie is attempting to send herself another message telling her not to get caught at the window by Finn, Big Joe walks by. He sees Callie at the window with the piece of paper taped to the window. He tells her to go to the door
She opens the door and asks him what he's doing there. He tells her that Finn left him a message telling him to that Callie and him (Finn) were leaving town and that he might be interesting in what Jasper was up to. He asks her about the blood stain on the window. He asks her if he can come in. She looks over at the note on the window and says "Sure. It doesn't matter. Tonight, none of this will matter." She opens the door and lets him come in. To his shock, he discovers the murdered Jasper and Finn. She says "I guess you have some questions for me." The final shot shows Callie being led away by Big Joe and the note "DON"T GET CAUGHT AT WINDOW" still taped on the window. The note falls off the window. As a result, Callie runs back to tape it back to the window, with Big Joe running behind her. A few seconds later, Big Joe comes back into frame, dragging Callie away. The camera takes a picture of the window, hinting that without the note taped to the window, everything will happen as it has.
THE END
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 the elderly tenant, "Mr. B", across the way has not paid his rent in two months, Callie goes to check 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.
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, as he usually 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 Polaroid gets him past his block. Based on what happened to Mr. B and notes in his journal, they realize 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.
In the end, Jasper fights with Callie and Finn, which ends with Callie killing Jasper. Finn realizes that Callie has been playing them both all along. She has been manipulating the photos to make things go well for her and Finn. Finn decides the only way to end the problems is to destroy the machine. As he does, Callie shoots him. She is discovered by a police officer and against her best efforts to leave a message for herself with a piece of paper, the paper falls off the window as Callie is led away. Since the piece of paper was not there when the picture is taken, everything will happen as it has.