The resourceful best friend and panicked boyfriend of a young girl in suburbia struggle to overcome a shady drug dealer, and the cops, in order to defeat the satanic forces possessing her.

I like that. Thanks!

I was thinking the opposite, I believe the Drug dealer is trying to saver her, maybe in love. The lead character doesn't know that and believes the Drug dealer is after the her friend to harm her. (A misunderstanding)

In the end it's the Drug dealers info that saves the GHB possessed character.

Ok. I see two options:

1) It's a crime story and the twist is that it's not a drug overdose, it's out right demon possession, as you say.

2) It's horror/occult. What's at stake is her soul. The main character's goal is to save her best friend's soul. Then, we get the first twist at the end of act two: It appears she's not possessed but has been the victim of a lethal dose of GHB. The priest is sent away, her symptoms lessen, and she goes to the hospital for treatment. But drug tests reveal that she has clean blood. Then, the demon returns for a final battle at the end of act three.

Whether it's soul or mortal life, the main character's goal is to save her best friend, because that's what friends are for. Do you think it requires something more concrete?