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Genre- Horror/Thriller
Plot- A young girl named Kristen awakens in a psychiatric hospital after setting a farmhouse ablaze, and finds herself stalked by a malevolent ghost in this psychological shocker from celebrated horror director. Badly battered and seemingly stricken with amnesia, Kristen forges a fragile friendship with fellow patients Sarah , Iris , Emily , and Zoey  as her compassionate therapist, Dr. Stringer , works to uncover the source of her mysterious condition. Later, at night, when the lights in her remote ward go dim, Kristen is confronted by an imposing phantom that seems intent on dragging her screaming into the darkness. Eventually, the other girls in the ward begin to vanish, one by one. Now, the harder Kristen fights to avoid falling prey to her shadowy pursuer, the more convinced she becomes that no patient who's checked in to North Bend Psychiatric Hospital ever comes out alive.

In the Plot Summary above and in the trailer you can see how it does not show how the story ends how that is a turn in it and a shock for the audience.
The story ends with the girl being the only one in the psychiatric unit in the hospital and none of the girls are in there with her so when it says 'no patient who's checked in to North Bend Psychiatric Hospital ever comes out alive' it is because no one else has checked in and the director has tricked you.
In the trailer you can just see how you get freaked out and there's no way you could tell that they are all her etc.

I think this trailer would help me for ideas for my trailer as i can see how the director does the work of the story line without giving too much away. 

Camerawork
At the start of the Trailer the camera work is effective as its approximately 2 seconds for each  camera shot to be shown. This makes the audience focus on whats happening. Its effective because it tells a lot about the story in only 6 seconds and this is essential for me to do in my teaser trailer as i wont have a lot of time. The establishing shot shows the psychiatric hospital giving us a insight to the story.

Mise-En-Scene
The clothing that all the rest of the girls are wearing as shes entering the ward is normal, they all look like normal girls with everyday clothing so nothing suggests that these girls have a reason to be in the psychiatric hospital. However the main girl 'Kristen' is in a uniform with her hair all messy etc. This is showing how she has a problem and is different from the rest.
The lighting is key in the film as on the ward there is always flickering making it look dark and mysterious