Need help with my plot?

I'm gonna lead towards two, and I'm gonna say that Sarah had always pulled attention from Beth, always stole the limelight, and she finally had enough, she uses the guy thing as an excuse and then catches Sarah off guard in a (cliche I know) dark alley, knocking her unconscious. She takes Sarah to an abandoned building, tapes her mouth shut, ties her up stabs her in both legs arms and in the chest and leaves her to slowly die. Then, hero Jack comes into the mystery going to the place where he meets Beth and they side up, Beth says she went a different way, turns out she had just gotten off the phone with Sarah's dad and is leading him to the interrogation as an act they pretend to knock out Beth, and leave them both in the alleyway. Jack wakes up and sees Beth "knocked out" he goes to her to wake her up, and notices a broken bottle behind a dumpster in the alley. This is where he gets his first suspicion about the kidnapping/murder attempt at first, he thinks of just a petty mugging but he knows, if that was true the mugger wouldn't have taken her with him. It must have been a rapist. He wakes up Beth and shows her the bottle which is cracked and bloody. She reacts oddly, And Jack feels awkward, but ignores it. They continue down the path, Jack finding little trails of blood until Beth turns on him, and the mystery is solved, he questions her,and some what interrogates her, but the cops were called by someone who saw, they take him into custody, but who would they believe, stalker boy, or teenage friend... then you can play around with how he gets out and finds her and stuff....