The film begins on halloween with a shot of the bustling school entrance. We then meet the five main characters Jordan, Alex, Gavin, Nessa and Katie as they walk through the school grounds. It is Friday and Alex produces a leaflet that he has been "given" about a local halloween party taking place that night. The teenagers are indecisive about whether to go so they go to the common room and flip a coin. Gavin says "Heads we stay in and watch a movie, tails we go to the party." Alex flips the coin and it lands on tails. The bell goes and they all go home after planning to meet at 9 to go to the party together.
At 9 o'clock they all meet at the corner of a street, it's dark. Katie and Nessa are there first and then Gavin, Alex and Jordan arrive separately. They walk to the party, the front door is open so they walk straight inside, shutting the door behind them.
They all walk into the packed main room and Katie, Jordan and Gavin go straight to the other side of the room to get drinks. Alex and Nessa stand on the other side and mingle. Nessa is holding her phone, she outs it down for a moment to look in her bag. When she looks up again her phone is gone. She just assumes that it has been stolen by someone at the party and isn't too bothered because it was cheap.
Moments later, out of sight and on the other side of the room, Gavin receives a call from Nessa's phone number. Gavin, Jordan and Katie are unaware that Nessa's phone has gone missing at this time. Gavin answers the phone and hears crackling and indistinct whispering. Assuming that it is Nessa and he just doesn't have signal, Gavin goes to the door to get outside. The door is locked, he tries another door, it is also locked, he then tries a window which is also locked.
Gavin tells Jordan and Katie that they are locked in. They feel a little uneasy and try to tell other party-goers. Everyone brushes them off in a trance-like fashion and carries on dancing.
The lights go out. Everyone gasps. There is a state of panic. "What's going on?" Someone feels a cold brush by their arm. A girl screams. Gavin: "Stop messing around guys. Turn the lights on!" A rustling sound. It sounds like Gavin is in pain. "What happened to the lights?" Katie in panic rushes to the light switch and frantically tries to switch it on. "It's not working! It's not working!" The light switch is on the off the button.
And then the lights come on. But the audience can see that the light switch is off. There is dead silence. Katie is still at the light switch. "Hold on! This switch is actually off!" Turns around to see that everyone else has gone and the other four are in a state of shock. Katie: "Where's everyone just cleared to?"
Nessa goes up stairs. "I need to use the bathroom." She opens the bathroom door. She sees Gavin lying face down in the bath with the shower on. "Gavin! Oh my God!" She pulls him slightly over. His face is completely deformed. Blood is dripping from his neck. All of a sudden she notices a large pool of blood in the bath. She screams: "Everyone come upstairs." Everyone attends. He tries to speak but he can't. They pick him up and take him to a bedroom. They lie him on the bed. They try to stop the bleeding with the bedsheets. He still can't speak. "What happened?" Then he dies.
Alex runs to the bathroom and throws up. Then when he looks back up in the mirror he sees a black silhouette behind him. He turns around straight away so it's only there for a split second and there's nothing behind him. He feels scared but he doesn't tell any of the others because he thinks it's all in his head.
They all go back into the living room to discuss what they are going to do next. Alex says that he's going to try to get some signal. And Katie says she's going to see if there's anyone else left in the house. Nessa is having a panic attack so Jordan stays and looks after her.
Cut to Katie walking through the corridor looking into rooms.
Cut to Alex walking into the bedroom. Sees a window a bit open but it's second storey so he can't jump out. He sits on the ledge and leans out of the window and he gets signal. He calls Tom who he saw at the party. "Tom! Where did you go?!".
"What do you mean Alex?" Alex then asks why everyone left the party and why they locked the five in. Tom explains that he was never at any party. Alex feels a sharp pain in his back, he slips and drops the phone out of the window before he can ask for help. He then makes his way back to the others in the living room.
Cut back to Katie looking into rooms. She enters a bedroom and sees someone sitting on a bed with their back to her. They are wearing a hood so it is unclear who they are... She walks towards the person and grabs their shoulder. The person turns around, their face is hidden, and they thrust the blade through her neck. They hold it there for approximately two seconds and then slice to the right out of her throat, leaving her neck dangling to the side half on.
Cut to Alex entering the living room as Nessa gets up to look for Katie as she is worried about her. She leaves the room.
Nessa screams, Alex and Jordan both run into the bedroom to see what has happened, Katie is in a pool of her own blood.
Jordan: OMG
He runs out the room to the living room and the rest follow him. Alex is the last to enter and locks the door without anyone noticing
Alex: Ok what the hell is happening?
Nessa: who is doing this what have we done (crying and hugging Jordan)
Jordan: did you get reception
Alex: yeh i called Tom but dropped the phone
Jordan: (Jordan eyes widen in disbelief) how on earth did you manage that
Alex: look at this (lifts up his shirt to see burn mark) something burned me and made me drop the phone, whoever or whatever is doing this is stopping us from getting in contact with anyone else.
Nessa: How the hell could you drop the phone what's wrong with you?! That was our only way to get out and now we're stuck, you probably did it on purpose
Alex: WHAT are you trying to say? That I’m doing this?
The group start to argue and accuse each other. Jordan finds a bloody hand print on the wall – "Hey guys look at this!"
Alex: it must be the killers, so whoever's hand fits must be the killer
Everyone hesitates as no one wants to go first. Alex goes first, then Jordan, then Nessa. Nessa's hand fits.
Jordan: Nessa??
Alex: it makes sense now, you found the bodies, and you started accusing people
Nessa: it wasn’t me I swear
Alex: she’s lying
Nessa: Jordan you know me, why would I do this, Katie’s my best friend
Jordan: I don’t know, you did find Katie and at the party i got a phone call from you
Nessa: what phone call? I lost my phone at the party
Alex: what did the person say?
Jordan: I didn’t hear it properly, it wasn’t clear, that's when all this stuff started happening
Alex and Jordan gang up on Nessa. Jordan and alex convince themselves that it was Nessa.
Jordan: we've got to kill her
Alex: what?!
Jordan: whatever's or whoever's making her do this, is going to kill us too!
Jordan and alex talk and decide that they have got to kill her.
Nessa: no, please it wasn't me
Jordan: stop lying, your hand fits you found gavin and katie and you made that phone call.
Alex picks up Nessa and ties her to a chair with some cable from the TV. Jordan and alex discuss how they are going to do it, Alex convinces Jordan to do it some how. Nessa still pleads with them to stop and is trying get away. She manages to untangle herself and gets up and picks up and smashes a bottle.
Alex: look she trying to kill us
Jordan walks towards her she stabs him in the arm, Jordan uses a chair to repeatly hit her until she is dead. Jordan goes towards Alex to tell him that Nessa is dead, Alex turns around and his eyes are black, Jordan realises that something is wrong with him.
Alex looks at the hand prints and so does Jordan. The handprint changes shape and Alex puts his hand on it, it fits.
Jordan realises that Alex is the real kill and he is possessed with something, he tries to leave the room but the door is locked. Alex charges at him, he misses and smashes down the door. Jordan runs out the room and Alex chases him.
Jordan picks up a corkscrew to defend himself and alex runs towards him. He jabs him in the eye. Alex grabs his eyes and falls to his knees and Jordan runs out of the room.
Cut back to Alex. Alex gets up. He thinks Jordan has gone outside so he unlocks the front door to look for him. Jordan isn't outside so Alex runs back into the house and runs upstairs. He gets to the top step and Jordan jumps out and pushes Alex down the stairs. He then pushes a chest of draws down and it lands on him. Alex is dead.
Jordan sees the front door open runs out. The film end with a front view of Jordan running down the street.