This plot is a bit unpleasant and has no happy ending to it. I would suggest it be used only in the "darker theme" type of games. It is mostly a morality play, who will the players help, the "innocent" man or the teen with no control over his actions.
Hook: The characters will be somehow drawn to a small Midwestern town to investigate some unusual deaths all of which have some aspect of the paranormal about them. Perhaps one of the characters relatives lives in the town or the events have come to the party's attention by other means.
Line: Three deaths have occurred in the small town, one death per night. The people are frantic, paranoid and terrified. All of the victims were young women from the city. Each girl was brutally murdered, literally cut apart in a ritual fashion by some sort of sharp object; a knife or sword. Each body was laid out inside some sort of magic circle drawn in chalk and lit with candles at the points. The townsfolk believe that the deaths were caused by Ernest Helt, an ex-convict who moved to the city a few months ago after being released from prison on parole after having served time for sexual assault on a child and murder. He has been taken into custody by the local law enforcement after a frenzied three hour escape attempt. The people of the city are just on the verge of extracting a little "mob justice" from Ernest. The players will have only a day or two to sort things out before Ernest is killed by a grieving father as he is transferred to a higher security prison pending trial.
Sinker: Ernest is actually innocent (in a sense). Since leaving prison, he has been working as a janitor and trying as best he knows to fit back into society. He is not a very intelligent or social man and has made no attempt to try to win over the people of the town who wish he would just move on. Ernest is a borderline alcoholic and tends to get extremely drunk and pass out most nights, he ran from the police because he knew they would accuse him of the deaths. The real killer is actually another teenager, Roger Stills, a young man who has become possessed by the spirit of a serial killer who murdered thirteen girls eighty years ago in an attempt to achieve immortality, and was torn apart by a wild mob after having been caught. The spirit is trying to recreate the events which happened in the past (figuring it worked well enough then it might work again) and is looking forward to seeing someone else take the fall. The parallels between the events will be obvious to anyone who searches the old newspaper footage.
Roger became possessed while camping out in the cemetery on a dare from some of the other high school kids, he mistakenly chose to camp over an unmarked grave (the body of the serial killer). Roger is a latent psychic and was easily controlled by the entity. The key piece of evidence is the machete which Roger used in all the killings, it will be found in a corner of his garage. Should the players drive the entity from Roger, he will remember almost nothing, as if he has been dreaming for the past few days. He will only come to realize what he's done if the players confront him with the evidence and force him to focus on the "dreams". Should he be sentenced for the murders, the police will find corroborating evidence upon investigation, it is likely that he will spend most of his remaining years in a psychiatric hospital or prison and Ernest will go free. Should the players not point out Roger as the killer, Ernest will be killed by a distraught father of one of the girls as he is being transferred to a more secure jail pending trial. If the player s are unable to stop the entity, it will bide it's time and leave town to take up the game elsewhere.