Curtain. On the stage there's a row of about forty heads, of natural size, on a long and narrow white board roughly chest height, arranged facing the audience with equal spaces between them from near the left end of the stage to near its right end. The heads are all identical apart from two features. First, the leftmost head is completely bald, the rightmost head has lots of hair on its scalp, and the amount of hair on the heads increases gradually and uniformly from left to right, so that it is hard to discern a difference between any two consecutive heads. Secondly, the colour of the heads changes from bright red on the left to bright orange on the right, again so gradually that it is hard to discern a difference between any two consecutive heads. Apart from the row of heads the stage is empty, with dark background.