Film Planning - Initial Plot Ideas

Initially, we wanted to copy 'A Stranger Calls' by having a party and a shadowy figure waiting outside. The shadow person would follow a person home and kill them, and we would crosscut between this and the party. The person's dying scream would be blended with the sound of a glass at the party falling to the ground and smashing. Although we all liked this idea, we also felt that it would be more suited for a film opening and not a trailer.

We then realised that we needed the person to have a motive and decided that the murderer-guy would be a friend of the girl hosting the party. Our first idea was that he wasn't invited to the party and he's bitter about that - which we then had to expand because that wouldn't be a good enough motive for murder without some backstory.

After some brainstorming, we made up a new idea that still had some elements of our original idea; a boy who's grown attached to a girl makes bad thing happen to her friends so that she pays more attention to him, which escalates into him killing her close friends.

We considered telling the story from the perspective of the boy. This would show him growing up with a girl who's like a sister to him but, as they get older, she starts to push  him away - which results in him trying to get revenge on her. To add a twist to our movie, we then decided to tell the story from the girl's point of view and make the bad things seem like a supernatural being's work - that finally gets revealed to be her childhood friend.