The film begins with a sleepover of children. They prank call people while playing the game Seventy Five. Meanwhile, their parents are in the other room having drinks. The rules of the game are that you must keep a random person on the line for 75 seconds, and they must believe what you’re saying. As the night goes on, the kids go to bed, and a man whom the kids recently called calls back, before jumping from a closet and killing all the parents in the house with an axe as the children hide in their bedrooms. Ten years later, Chuck is murdered in his house by an unknown figure. Two detectives, Detective Anne Hastings and Detective John Criton discover Chuck was one of the children involved in the Waley murders 10 years previously. They begin an investigation and find more of the survivors have been murdered. Meanwhile, Brandon is throwing a party at his fathers secluded mansion. Brandon invites his ex-girlfriend, Karina, so he can try to get back together with her, but she insists that her group of friends also come, including Marcus, Roxy, Shawn, Kareem, Scott and Jody. As the group arrive and the party starts, Brandon and his friend Cal show everyone around, revealing that the house is filled with cameras which can be monitored on screens in the monitoring room, due to the house previously being used as a reality show set. After a few hours of partying, Marcus suggests a game of Seventy Five. Various people take part, until one caller murders someone for the group to hear. They all decide to not answer the phone and continue with their night. As the party finishes and most people leave, Karina and Brandon reconcile. Becky and Julie stay up partying with two boys. However, the killer soon arrives at the house and decapitates Becky, before killing the boys and Julie. The killer proceeds to decapitate a boy in the hot tub before drowning his girlfriend. Kareem witnesses the murders and rounds up Roxy, Marcus and Anna to leave. The group split up to warn the others. Marcus and Anna find Jody and Cal, however they are soon attacked by the killer who murders Anna, while the others flee into Brandon and Karina's room. After Kareem and Roxy arrive with an unconscious Scott, who Kareem accidentally knocked out, the group lock themselves in the room. Brandon blames Marcus for the murders, causing a fight to break out. After a while of waiting, Brandon and Karina leave to retrieve keys for Brandon's car, while Marcus and Kareem search for Shawn. The killer soon attacks Brandon and Karina, and Brandon is eventually axed in the back, killing him. The killer then throws Karina off the balcony, however she survives and runs into the monitor room to hide. Meanwhile, Cal goes outside to try and hot wire a car. As he succeeds, the killer appears and beats him to death, although he does manage to summon help to the house. Marcus and Kareem return to the room only to find it empty, before discovering Roxy has been killed. They find Scott, but are soon attacked. However, Marcus and Kareem manage to overpower the killer and pin them to the ground. As Kareem urges Scott to kill him, he instead murders Kareem. Marcus hides in the monitor room with Karina, watching in horror as Jody and then Shawn are murdered. Scott soon comes to the monitoring room, with his accomplice, who is revealed to be an inmate from the mental hospital they both recently escaped from. He goes on to reveal that he is, in fact, Scott's twin brother, William, and that he murdered Scott before they left for the party. William tells Marcus he blames him for the deaths of his parents all those years ago as he was the one that wanted to play Seventy Five. William then turns on his accomplice, stabbing him, before a fight breaks out between him, Karina and Marcus. Eventually, William stabs Karina to death. While Marcus swings the axe to kill William, Detectives Anne and John arrive and shoot Marcus, believing he is the killer. As Anne and John comfort William, the accomplice rises with an axe and swings it towards the detectives.
