Treatment (short and longer version)

Short version: 

Teenagers/victims go into woods to party. They pass a small burial ground purposefully destroying it. Kurt becomes possessed. Kurt shows signs and Clara asks if he's okay then take to walking him home. They 'get busy' before Kurt strangles her to death. Wade Terrence and Alyssa find the body then split up to find Kurt (see if he's okay/alive). Alyssa passes burial area discovering a key necklace attached to tree ( unlocks box in the hollow of the bottom of the tree) Terence decides to kill Wade using a beer bottle. Terence tries to dispose body but is found by Kurt and killed by knife to the throat. Alyssa returns and sees Kurt over wade and Terence's bodies. She and Kurt fight. She kills him with the fire poker through his neck. Her body then becomes possessed making there no final girl resulting in an open end. 

Long version: 

A small group of teenagers - Alyssa, Clara , Lucas , Wade and Kurt - Go into the woods to party ; avoiding clean up and parents. While carrying their equipment for the night they pass a small open space with a set of runes in the middle beside a small tree , or more likely a burial place. After desecrating the area they leave to go to the intended area. (not knowing Kurt is possessed). When they arrive Kurt begins acting strangely – Clara asks him is he's feeling well .  Kurt (the spirt) says no. Clara begins to take him home after telling the group. They begin 'getting busy' on the way back  when Kurt(the spirit) puts his hands round her neck and begins applying pressure until she chokes to death then collecting his knife and slicing the spiral goddess into the hollow of her neck. When the rest of the group leaves the party area they pass Clara's Body. They worry about Kurt's health and decide to split up to find him. While walking Alyssa passes the burial area discovering a necklace from the tree seemingly covered in blood (with a key attached) which unlocks the box in the grave. Terrence decides within the commotion to join in killing for revenge. He follows wade and kills him using his empty beer bottle to the back of the head – then using the shards to cut his jugular. Dragging him back to the fire to dispose of the body where he is found by Kurt (who looks to be decaying) and killed – by the ritual knife to the throat. When Alyssa returns she finds Kurt looming over Wade and Terrence's bodies.  He stands turns and advances on her. While fighting for her life Alyssa picks up the fire poker from next to her rams it through Kurt's neck subsequently killing him. The 'white' goes out of his eyes transferring to her resulting in an open end