Rebecca (Teresa Palmer) becomes concerned when her mother, Sophie (Maria Bello), begins to suffer from depression again and starts talking to an 'imaginary friend'. She is also worried for her little brother, Martin (Gabriel Bateman), who is beginning to suffer from insomnia and behaving strangely. She soon learns why this is happening, however, when she sees for herself the creepy apparition which moves in the dark around them...
The short had a great premise and truly gave me the wiggins. The creature is only able to be seen in the dark and by flicking on and off the light, you can see it slowly (and yet somehow also quickly) approach you. It's menacing and effective.
As a feature length film, however, this effect loses some of its impact and the film began to feel somewhat gimmicky. However, as a whole the film is quite enjoyable in a simple, jump-scare-by-numbers-horror way. The characters are good, but they're not given enough time to develop effectively and there's perhaps too much going on in the back story to be cohesive.
The thing that worked so well for the short was its simplicity and this felt a little lost in the feature length film. In an attempt to create a personal origin story for the shadowy creature, the story lost some of its simple, effective mystery around the creature. I feel that sometimes horror monsters don't need to have their motives explained; they just need to be scary. A sympathetic backstory can be effective, but this explanation in "Lights Out" felt forced into the story.
My advice is by all means see this film, then go re-watch the short to remind yourself how good the premise really was.
[Image: New Line Cinema, et al]