ending

Cara shows Lauren a place where the other girl she was rooming with, the one with the darker hair, can hide, and then Lauren runs out into the hallway, smashing all the lights with a broom.
She comes face to face with Spence, and she starts chanting, nearby the broken elevator, trying to make Spence take possession of her so she can then kill herself, and in the process, kill Spence.
Spence then tries to strangle her, but Grant hears the noises, and comes into the hallway, and starts chanting himself. He then runs towards Spence, and they collide, and Spence then possesses Grant. Grant then runs towards the elevator shaft and jumps in killing himself and Spence.
Then you see Cara's ghost walking away in the hallway, and dissolving.
The police comes, and lauren tells her story, and ask the cops to take her to Cara's sister, which she gives the cookiejar she found with Cara's stuff, saying Cara wanted her to have it.
That's it, basically.