Ten people are secretly filmed as they witness what they believe to be a real crime - a knife attack in a Manchester pub. But when they are later interviewed by the police, their memories are radically different to each other's and to what really happened. In an extraordinary experiment with the Greater Manchester Police, the problem of eyewitness recollection is dramatically brought into focus, as are the remarkable techniques used by the modern police to counter our unreliable memories. Narrated by Philip Glenister.