Moving pictures

'Holy Wood is a different sort of place. People act differently here. Everywhere else the most important things are gods or money or cattle. Here, the most important thing is to be important.' Alchemists have always thought that they can change reality, shape it to their own purpose. Imagine then the damage that could be wrought on the Discworld if they get their hands on the ultimate alchemy: the invention of motion pictures, the greatest making of illusions. It may be a triumph of universe-shaking proportions. It's either that or they're about to unlock the dark secret of the Holy Wood hills - by mistake...