The Purge is a film loosely based around the "what if" concept of crime being legal for a 12 hour period every year; The idea being that everyone is allowed to purge their anger and hatred at the same time, thus allowing the remaining 364 days to go by unspoiled. Rather than choosing to continuously depict scenes of mob mentality however, these are contained in the opening credits and the story itself focuses on the Sandin family, whose night from hell which begins when Charlie, the young son, offers refuge to a homeless man being hunted. Although the film gives a welcome return to an actor who seems to have been gone from our screens for quite some time, Ethan Hawke as the Sandin's father James, the appearance of Lena Headey is surprisingly not as agreeable as you might think. This is not to say that she gives a bad performance, and with strong roles such as Sarah Connor and Dredd's Ma-Ma on her C.V. you can see why she was cast, but the character of caring mother Mary would have benefited from an actress who appears more at home in white picket suburbia than when inevitably dual wielding handguns. Siblings Charlie and Zoey are also efficiently played by Max Burkholder and Adelaide Kane respectively, even if the teenaged and short skirted Zoey does suffer from being played by an actress obviously in her twenties. Although The Purge is far from the only film to do this, being cast opposite actual teenager Burkholder only serves to make Kane's difference more noticeable. By far the most intriguing character is that of Edwin Hodge's unnamed "Stranger" however, a victim in almost every sense of the word, and who isn't even afforded an adjective in the credits. His mystery is furthered by his almost perpetual silence, and visual clues are the most we have to go with; dog tags offer a hint as to his unexplored background, and his skin colour also adds another angle to the film's examination of who is blaming who for the crime that the titular purge supposedly eliminates. While the pretext of a twelve hour crime spree makes itself known but soon leaves the film to tell a family story, it does allow the film to deal with a number of wider issues, not least that of rich vs poor. It's not giving too much away to say that the villains of the film are wealthy, smart, and educated, something that Rhys Wakefield's oddly described "Polite Stranger" freely admits to, and the question of whether or not the purge is instead a way of ridding America of the homeless and unemployed is one that the film doesn't leave unmentioned. Hunters speaking as though it is their duty to kill those they have a hatred toward (and often thank them for their sacrifice when doing so) aside, the fact that the film's tension relies on a home invasion to get at someone seeking refuge means that the film can far too easily be described as simply as Straw Dogs with social commentary. Although it is refreshing to see a film released during the summer blockbuster season that neither follows on or is specifically adapted from something pre-existing, the film's influences are all too obvious and those wishing to see something wholly original may leave the cinema wishing that more was made of the initial concept itself. Despite the fact producer Jason Blum has worked on films as varied as The Reader and The Tooth Fairy, it is clear to see why the trailer lists Paranormal Activity as The Purge's most favourable comparison. While it rightfully leaves the found footage concept to the horror genre, I can't remember seeing a thriller with such a liberal use of a shakey cam, and those watching the film from the front row should probably be given a Cloverfield style motion sickness warning. Forgive me if I seem to be giving The Purge a bad image, it's not that it's a bad film, just one that never reaches its potential. While the decision to tell the story of a nationwide event by focusing on a single family is commendable, the allegory it tries to express isn't as nuanced as it could be, and only just escapes being preachy. Perhaps unsurprising from a Michael Bay film (yes, he is one of the films producers, and no, I wouldn't have advertised it either) the house of Sandin seems to rely on its being built from bricks of stock elements rather than strengthening its unique foundations. The Purge is out now in cinemas.