Over the period of display 100 city people – who are obviously not present in the square – also come and go on-screen, their gaze aligned with the viewpoint of the CCTV camera. The citizens looking out have a vapourous, brightly coloured form, differentiating them from any live, surveilled observers with whom they share the screen. Everyone on-screen – whether actually present in the square or not – is "ghosted" by a mixing process. Only the paved square appears solid.

The spectral figures who appear in the live scene were recorded during a video shoot on the evening of 27 October 2002, when around 100 Bradford people gathered around the fixed camera, and dispersed, following simple choregraphies. A few local celebrities are present in the recorded groups, but on incorporation into the work every likeness is treated in exactly the same way. Extra depends entirely on the participation of the 100 volunteers, although the final work leaves open the question of which participants – the live, the recorded, or all – might be "extras" in the film-production sense of the word.

Over the intended three-year lifespan of Extra it is expected that some viewers who participated on 27 October 2002 will return, to briefly share the screen with their younger, ghosted, selves. The experience of such viewers will differ from that of a visitor with no personal memory of the creation of the image. Considered in the context of the nearby statues of Queen Victoria and J. B. Priestly, it is hoped that Extra can both entertain and encourage discussion about the nature of public commemorations and monuments: about whose existence is remembered, for whom, for how long, at whose behest, and with whose consent.