Plot to the Opening

A group of friends are out camping in a field. The scene starts with an clip of the friends around the fire having a beer and being merry. It cuts to one of the female members staggering off across the field to find somewhere to go to the toilet. She is drunk and doesn't really know where she is going. Her friends are calling her back but she isnt listening and continues to venture into the woods.
She is beginning to feel like she is being followed. She is looking around and the trees are rustling and brushing past her as she picks up her pace.
She begins to run. Through the trees she can see a light and begins to run towards it. She reaches a light which is on in an old abandoned caravan. The door is open and she runs in slamming the door behind her. She slumps against the door and looks about. Her heart is thudding and she is gasping for breath. She looks towards the living area of the caravan and takes in the scene around her. - there is furniture overturned, stuff strewn everywhere, blood all splattered up the walls and then her eyes fix on the body of a young man/woman who is dead on the floor.
She lets out a scream and it then cuts to her friends around the fire hearing this and then back to her backing away from the body. With a flash of light cuts to a mental image she has of a hooded figure with an knife, stabbing the woman in the room.
The opening ends with her hiding in a room in the caravan with the hooded attacker appearing in the window so that the audience can see him but she does not know he is there.