Rebecca (Theresa Palmer) is forced to return home to her estranged family when her little brother Martin begins seeing the same ghost that tested her own sanity as a child. As she works to unlock the truth behind the terror she soon comes face to face with Diana, an entity that has an attachment to her depressed mother, Sophie (Maria Bello).

You know you've got a pretty good concept for a horror movie when the two minute short that you entered into a festival and didn't even win ends up becoming a viral sensation and catching the attention of Hollywood. David F. Sandberg and wife Lotta Losten's short film Lights Outwas spotted by James Wan (director of Saw, Insidious and The Conjuring) and soon the couple were upping sticks from their native Sweden and moving to Hollywood to develop Lights Out as a feature.

Screenwriter Eric Heisserer was brought on board to flesh out a story to attach to the short's concept about a monster that can only be seen (and move around) in the dark. The resulting plot becomes about Rebecca (Palmer) who is forced to deal with literal ghosts from her past when she discovers that her little brother Martin (Gabriel Bateman) is beginning to see Diana, the same creepy monster lady that haunted her dreams as a child. At least she assumed they were dreams. Turns out Diana is very real and is pals with her depressed mother, Sophie (Maria Bello). She's also quite protective of Sophie and is prepared to go to extreme means (like murder) to protect their friendship.

Sandberg proves that he's got the chops for horror, building on the impressive short with some jumpy set pieces. An early sequence in a warehouse that re-creates a scene from the short works really well and provides a great base for the film to build upon. Unfortunately, the rest of the film never really matches the same level of terror. Diana certainly proves to be a creepy presence, however the longer the film goes on (and the more we see of her) the less terrifying she becomes. To the point where by the film's conclusion, scenes intended to fright are quite ineffective.

Some lapses in the film's logic cause drawbacks too. For instance it's established early on that Diana can knock off the electricity but waits until the film's climax to use this to her advantage.

The film's cast keep things interesting though. Palmer is very engaging as Rebecca and her relationship with Bello feels authentic despite the limited screen time the two have together to establish it. Indeed with a lean running time of 81 minutes, the entire cast have very little time to scratch beneath the surface of their characters and yet they make a compelling enough argument for us to want them all to survive which is rarely the case in horror.

Overall though, Lights Out is a pretty average horror that will quickly be forgotten. That is until the inevitable sequel comes out.