Alice definately killed her sister...Spoiler

During Aunt Annie's stabbing, Alice was in the basement and she must have seen the yellow-coated figure and then hid, thinking this was Karen. She quite possibly believed what Alphonso had previously warned her about happening - Karen not resting easy and coming back from the dead.

Absolutely no way. Just one killer, not two.

Yup,

The old lady killed Karen because the Father gave her the cross instead of her. Also, her daughter died the day of her first communion years ago.

Or.....

Alice did kill Karen. Tredoni then went on her own killing spree against the sinner parents. She attacked Annie, thinking it was the mother. When Tredoni ran out of the complex, she snuck out through the basement, and encountered Alice. Alice believed it was Karen, back from the dead, looking for vengeance. Alice would've had Karen's cross necklace in her collection, and then Tredoni probably took it at this moment.

The other clue that Alice killed her sister, while Tredoni did everything else, is in the MO. Karen was strangled and then set on fire, while the other victims were all stabbed by a knife that was carried around in a bag.

I just find it funny how so many people on this board are quick to say "Tredoni did it" without considering any other possibilities.


Welcome to Fright Night....for real. 

possible spoilers




If you pay close attention in the beginning, the masked killer who strangles Alice is a lot larger than her, its just hard to notice it because of the camera angles. Take a close look when the killer is stuffing Alice inside that wooden chest and even kneeling down you can tell the killer is a grown person. :)

Listen to the audio commentary. The ending of the film when Alice is walking away. The OP could have a point. I may not agree, but just listen to the audio commentary.