The wind howled. Lightning stabbed at the earth erratically, like an inefficient assassin. Thunder rolled back and forth across the dark, rain-lashed hills. The night was as black as the inside of a cat. It was the kind of night, you could believe, on which gods moved men as though they were pawns on the chessboard of fate. In the middle of this elemental storm a fire gleamed among the dripping furze bushes like the madness in a weasel's eye. It illuminated three hunched figures. As the cauldron bubbled an eldritch voice shrieked: 'When shall we three meet again?' There was a pause. Finally another voice said, in far more ordinary tones: 'Well, I can do next Tuesday.' Through the fathomless deeps of space swims the star turtle Great A'Tuin, bearing on its back the four giant elephants who carry on their shoulders the mass of the Discworld. A tiny sun and moon spin around them, on a complicated orbit to induce seasons, so probably nowhere else in the multiverse is it sometimes necessary for an elephant to cock a leg to allow the sun to go past. Exactly why this should be may never be known. Possibly the Creator of the universe got bored with all the usual business of axial inclination, albedos and rotational velocities, and decided to have a bit of fun for once. It would be