A semi-transparent mirror hangs in the centre of a long, symmetrical space. Two chairs are positioned symmetrically on either side of the mirror. Over the mirror hangs a swinging lamp that illuminates the two sides of the mirror alternately. Depending on the direction of the light, the mirror is either reflecting or transparent. Owing to the symmetrical configuration of the space and the chairs, the viewer sees him/herself and the other people in the room alternately disappearing and reappearing. Sitting symmetrically in the chairs, two viewers see their reflection in the mirror changing into the other person in time with the swinging of the lamp.