A film that is tricky to review in part because it involves skirting around the central mystery that is best left discovered by a viewer first. The opening part of the film sets the scene brilliantly creating a sense of unease and uncertainty. Equally, the film recognises that a savvy audience will work out the central mystery quickly and therefore doesn't waste time trying to prolong it, putting the solution front and centre early on. The film is far more interested in exploring the impact that this has on the character(s) themselves, taking an ultimate "what if" issue that feels increasingly topical and tackling issues of corporate greed and profit over morality and ethics as well as exploring familiar science-fiction tropes of identity. Rockwell is key to the film with a fantastic performance throughout. Cleverly the film still maintains a sense of unease towards Spacey's homage to HAL from 2001, the stability of the central character (and thus our own belief in the solution) and a certain other character's loyalties and intentions that is best left discovered by the audience. As a result of some fantastic production design and careful use of visual effects, the filmmakers have made great use of a limited budget to create a believable setting. One of the best films of 2009.