The Final Plot

Two teenage friends (the protagonists) are kicking a ball around in a forest. There is also a woman walking her dog in the background.

As one of the teenagers answers a phone call, he kicks the ball slightly off course, meaning that the other person has to go collect it.

When the ball has been collected the other teenager turns round and drops his phone in disbelief and stares, in the shot, the person collecting the ball then turns round, and stops as well. Just before this, there is a slow motion shot of the slide up phone landing on the floor.

The camera tracks round the two of them to the back of their heads, and in the distance you see what they were surprised about.

They see the immobile body of the dog walker sprawled across the forest floor with the dog sniffing around the body. They see a plain white mask with a smeared red handprint diagonally across on the face of the mask.  

As the two look on, they see a dark figure (the antagonist) strolling casually away from them, further on in the woods. The person then turns round slightly and stares at the protagonists for what seems like an eternity, and the protagonists notice that he is wearing the same mask, only without the handprint. 

The camera zooms-in in cuts to a close up of the eyes of the mask on the antagonists, as he turns away the shot is blackened from his hooded top, the title credits then come in.