NOTE: This spoiler was sent in by Lightningstrike.
The movie begins with black background and orange text shows up on the screen saying the following (accompanied by deep voice over):
"On February.11, 2005, Kristen McKay and James Hoyt left a wedding reception to go to the Hoyt's family cottage for a romantic getaway"
"The events that followed are not entirely known"
The scene opens with an empty cottage and shows two Mormon kids standing in the front door. This is then accompanied by a 9-11 recording in the background, where the voice of a kid named Jordan is crying and talking about how 'There is so much blood" and that "He doesn’t know where he is." Shots in the empty cottage include a shotgun on a countertop, blood on the floor, blood splatter on the wall, rose petals on the floor next to a velvet ring box, and a large hole in the front door.
Cut to next scene, you see Kristen (Liv Tyler) and James (Scott Speedman) driving their BMW in the rain towards the cottage. You can tell that there is some kind of angry/sad tension between them but the reason isn’t given as they drive in silence. They arrive at the cottage and walk in the door where James proceeds to turn on the lights and you can see that he had intended to surprise Kristen with rose petals all over the place, soft music and a bottle of champagne. James says that he had come up earlier to get the place ready. She says it looks lovely, but there is still that sadness about them. James leads Kristen to a bedroom and says that she can have this room and he'll be down the hallway. Kristen gets a bath ready, while James makes a phone call in the living room to his friend Mike, that everything hasn’t gone well and he needs him to pick him up when he wakes up (IMPORTANT).
Cut back to the wedding reception; you see Kristen sitting at a table laughing and talking with some other guests, and James enters the room and sits next to her and after some loving kissing and chitchat, he asks her to come outside with him. Once outside he professes his love for her and proposes to her by showing her the velvet box (from the first scene). She looks at him with sadness, and then it cuts back to the cottage. It has become evident that she said No, and that’s what the awkwardness is about.
Back to the cottage, where we see James sadly eating ice cream at the kitchen table, as Kristen enters the room. There is a brief sad conversation between the two of them where Kristen says that she just isn’t ready yet. James says that it is probably not a good idea for them to go on the road trip they had planned and that Mike will be there to pick him up in the morning. After some tears from James saying that he can’t take the ring back and still wants her to have it, she takes the box from him. James stands up and Kristen comes to him and hugs him saying how sorry she is. This hug gets more heated as they kiss and their hands are everywhere and James slips off her panties as she fiddles with his belt buckle. They are just about ready for sex when there is a very loud knock at the door (This is where it all starts).
They go to the door and open it to find a young girl (15-17) shrouded in the darkness of the porch. She asks if "Tamara is there." James says that there is nobody there by that name. She asks if they're sure and they say yes. James attempts to turn on the porch light to see her face, but it doesn’t work. They close the door, and James reassures a nervous Kristen that sometimes people get turned around in here and that she'll be fine. James then re-opens the door to see if she needs help but she is nowhere in sight. James fiddles with the porch light and screws the bulb further in and it turns back on.
Kristen is visibly shaken up by this whole ordeal and wants a cigarette but the package is empty. James offers to drive up the road to the store to get some since he needs to get some air (side note: they tend to split up a lot throughout the film).
James leaves in the car leaving Kristen there, after lighting her a fire. Kristen opens the velvet box and after staring at the ring thoughtfully, she puts it on her ring finger and looks at it sadly. After about 5 minutes of her in the house, there is an identical loud knock at the door again. Kristen initially ignores it purposely but after persistent knocking she goes to the door and asks through the locked door "who is it?" The girl's voice again asks if Tamara is there, and Kristen responds that you've already been here, and she asks are you sure and Kristen says yes, and then there is silence.
Kristen then becomes aware that there is smoke billowing from the fireplace as if someone had closed the flue. She tries desperately to unstick the flue but then the smoke detector goes off so she gets up on a chair and after much difficulty she knocks it off and the beeping stops.
There is more loud knocking at the door and the windows, and now Kristen is seriously freaked out. She attempts to use her cell phone to call for help but it is dead so she plugs it in to charge it only to find that there is no service. She then proceeds to use the home phone to call James and pleads with him to come back since the girl came back and is knocking and scaring her. She asks him to stay on the phone with her till he gets back, but then the phone line goes dead. She goes to the window and opens it only to be greeted by a masked face staring at her in the window. She jumps back and runs to another window and looks out to see the young girl from before standing out in the front yard amongst the trees, only she's wearing a mask now. Kristen immediately rushes to the kitchen and tries to find a knife to protect herself with. While she is searching the audience gets a shot over her back to see a man in a suit and tie with a hood-mask over his head appear from the shadows of the living room and watch her. She finds a large butcher knife and turns around, only of course now the hooded man is gone. There is knocking and pounding from all over the house and she hears a window break, and then rushes into her bedroom where she attempts to hide under the bed, only to find that she can't fit. After successfully breaking the lamp in the room (cutting her hand in the process), she hides behind the bed. After a few seconds, she hears the front door open and footsteps. The audience gets momentarily freaked out until the man rounds the corner and we see that it is James back again. Kristen immediately freaks out on him, crying and babbling about what has happened since he left. James is skeptical of the masked figures she claims to have seen. She says that she just wants to leave with him. The audience gets a shot of her cell phone now burning in the fire. James asks her where her cell is and they can’t find it, and Kristen freaks out some more. James calms her down and they go the front door, where she waits for him in the doorway while he goes out to the car to get his cell phone. The car is smashed in, windows broken and tires slashed. James attempts to turn on the car to see if it can still move but is then greeted by another masked figure standing in the headlights. James gets out of the car and yells at him/her, "WHAT DO YOU WANT?!" He/She doesn’t answer and then James runs back into the house and bolts the door behind him, where Kristen greets him. They pull back the curtains only to see the masked young girl swinging on the swing set (very creepy). They pull back the curtains in the bedroom only to find the word 'HELLO' repeatedly drawn on the window in red lipstick. They then make a run for the car and get in and attempt to pull out of the driveway only to be rear-ended by an old rusty truck.
It becomes evident at this point from the people around them that there are three people doing this to them (a hooded man in a suit, a woman in a red shirt with a Japanese mask, and the young girl also wearing a Japanese mask). They run back inside the house, where James then runs around the house, searching for and eventually finding a hidden shotgun (with no shells). The front door starts rocking again and James and Kristen stand in the front hallway, and then there is a crash as the hooded suited man starts to ax down the door. James and Kristen run back and grab the piano and push it against the door to buy them some time. Then they rush to the bedroom where they rummage through the closet and James eventually finds a box of shotgun shells. After clumsily loading the gun they return to the door, which now has a large hole in it. The hooded man's face then appears in the hole where James proceeds to unload a shot tearing the hole in the door even bigger. They then rush to the bedroom and lean up against the bed with James pointing the shotgun at the door.
It is at this point that a black Jeep pulls up out front to reveal...Mike, the guy that James had called to come and pick him up. He's here early. Mike unsuccessfully tries to call James on his cell phone. Mike gets out of his Jeep and walks up to the house, and is greeted by the strange sight of the busted car and rusted old truck. He walks through the now shotgun-destroyed front door and enters the house.
Back to James/Kristen perspective and you see that they hear Mike's footsteps, and think that he is one of the bad guys (you know this is going to end badly). Mike makes his way down the hallway, and you see that the hooded man is silently following behind him with an axe. Mike never turns around and walks into the bedroom doorway only to get a shotgun blast to the face from James that takes off half his head. There is momentary silence as James moves out into the doorway and realizes that he just killed his best friend. Crying and wailing from both James and Kristen at this point.
After the crying stops, James says that he's going to go out to the barn where there is an old radio that they can use to call for help and that she should stay here (splitting up again). They pull back the curtains in the living room to reveal the word 'KILLER' written in lipstick on the window. James, with the shotgun begins to stalk through the darkened forest to the barn. He gets down on his belly when he reaches the halfway point as he sees the red-shirt masked woman come out of the barn with a large flashlight and she searches the property, eventually finding James with the light. James is about to shoot her, when you hear loud footsteps and James turns around to see the hooded man jumping at him. A shotgun blast is heard and the screen goes dark.
Back to Kristen at the house, who heard the shotgun blast. Kristen then gradually makes her way to the barn, avoiding the 2 stalking masked figures throughout the forest (the hooded man is not among them and James is nowhere to be found), and taking a nasty fall where she injures her ankle. Once inside the barn, we see from Kristen's perspective that the axe is missing from its spot on the wall. Kristen makes her way to the radio where she attempts to call for help. Just as she's getting a signal, the red-shirted masked woman starts smashing the radio with a blunt instrument of some type. Kristen screams and limps/crawls out of the barn. We see that their car is on fire (assumingly done to illuminate the surrounding area), as Kristen runs back into the house and hides in the pantry in the kitchen (we still don’t know what happened to James).
From the pantry Kristen peers through the crack and sees the hooded man silently enter the kitchen and walk around, where he eventually sits down at the kitchen table for a moment breathing heavily (sounds like he has asthma-wheezing). After a moment he gets up and walks out of the room. Just as Kristen is breathing a sigh of relief, the masked young girl's face appears in the crack and there is a struggle as she attempts to pull Kristen out. Eventually the struggle stops and the young girl disappears. Kristen emerges from the pantry and backs into the kitchen where she turns around and sees the masked young girl fingering the butcher knife that was left on the dining room table. Kristen rummages around in the drawer trying to find something to defend herself with, and pulls out a carrot peeler/small knife. It is at this point that the hooded man drags James, still alive and bloodied into the kitchen. He sees Kristen and yells at her to run. She attempts to run down the hallway but is hit over the head by the masked woman. The hooded man then drags a semi-conscious bloodied Kristen down the hallway (leaving a trail of blood from her head wound), who unsuccessfully tries to grab onto things to stop it. The screen goes black.
Cut to next morning, birds cheeping and the sun is out. We see Kristen and James tied up next to each other in chairs as the three masked figures look at them. Kristen asks why they are doing this to them. The young masked girl replies simply, "Because you were home."
All three of them then take off their masks and hood respectively, and you never see their faces, but you know that James and Kristen see them. James and Kristen plead with them for their lives, with tears streaming down their faces, but it doesn’t work. Knowing that they are about to die, they grip hands where James sees that Kristen is wearing the ring. He looks at her with a weak smile on his face and she cries and whispers that she loves him, and they share one last kiss. The woman then proceeds to slowly stab James in the stomach, followed by the chest, and the side. James still manages to live through all of this, still pleading with them to stop after every stab. He leans against Kristen as they then proceed to stab her in the side, and the screen goes black.
Cut to the two Mormon boys from the beginning, and they are walking down the road with their bikes, holding pamphlets in their hands (obviously going door to door). The rusted old pick up pulls up next to them, with the three unmasked figures in the car. The young girl gets out of the car and walks over to them, and asks if she can have one of their pamphlets. The younger boy asks her if she is a sinner. She says quietly, "Sometimes." He hands her a pamphlet labeled "Christian Living" and gets back in the car, where the man says, "It will be easier next time," and they drive away.
Now we are back where we were at the beginning of the movie, with the same shots of the now destroyed house. The two boys come upon James' bloody corpse (eyes open staring vacantly at the wall). They then come to Kristen, lying in a pool of her blood of the floor with her eyes closed. The boy touches her on the shoulder and her eyes pop open and she screams...
Fade to black...credits roll.