'It's a kind of magical light. Right. Could we just get more towards the point a bit?'
'I have heard it said that dark light is zer original light from vhich all other types of light came--'
'Otto!'
He held up a pale hand. 'I haf to tell you these things! Haf you heard the theory that there is no such thing as zer present? Because if it is divisible, then it cannot be zer present, and if it is not divisible, then it cannot have a beginning which connects to zer past and an end that connects to zer future? The philosopher Heidehollen tells us that the universe is just a cold soup of time, all time mixed up together, and vot we call zer passage of time is merely qvantum fluctuations in zer fabric of space-time.'
'You have very long winter evenings in Uberwald, don't you?'
'You see, dark light is held to be zer proof of this,' Otto went on, ignoring her. 'It is a light vithout time. Vot it illuminates, you see... is not necessarily now.'
He paused, as if waiting for something.
'Are you saying it takes pictures of the past?' said Sacharissa.
'Or zer future. Or somevhere else. Of course, in reality zere is no difference.'
'And all this you point at people's heads?'
Otto looked worried. 'I am finding strange side things. Oh, zer dvarfs say that dark light has odd... effects, but zey are very superstitious people so I did not take that seriously. However
He scrabbled among the debris on his bench and picked up an iconograph.
'Oh, dear. Zis is so complicated,' said Otto. 'Look, zer philosopher Kling says zer mind has a dark side and a light side, you see, and dark light... is seen by zer dark eyes of zer mind
He paused again.
'Yes?' said Sacharissa politely.
'I vas vaiting for zer roll of thunder,' said the vampire. 'But, alas, zis is not Uberwald.'
'You've lost me there,' said Sacharissa.
'Veil, you see, if I vas to say something portentous like "zer dark eyes of zer mind" back home in Uberwald, zer would be a sudden crash of thunder,' said Otto. 'And if I vas to point at a castle on a towering crag and say "Yonder is... zer castle" a volf would be bound to howl mournfully.' He sighed. 'In zer old country, zer scenery is psychotropic and knows vot is expected of it. Here, alas, people just look at you in a funny vay.'
'All right, all right, it's a magical light that takes uncanny pictures,' said Sacharissa.
'That's a very... newspaper vay of putting it,' said Otto politely. He showed her the iconograph. 'Look at zis vun. I vanted a picture of a dvarf vorking in the Patrician's study and I got zis.'
The picture was a wash of blurs and swirls, and there was a vague outline of a dwarf, lying down on the floor and examining something. But superimposed on this was quite a clear picture of Lord Vetinari. Two pictures of Lord Vetinari, each figure staring at the other.
'Well, it's his office and he's always in there,' said Sacharissa. 'Does the... magic light pick that up?'
'Maybe,' said Otto. 'Ve know that vot is physically zere is not alvays vot is really zere. Look at zis vun.'
He handed her another picture.
'Oh, that's a good one of William,' she said. 'In the cellar. And... that's Lord de Worde standing just behind him, isn't it?'
'Is it?' said the vampire. 'I don't know zer man. I do know that he vas not in zer cellar ven I took the picture. But... you only have to talk to Mr Villiam for any length of time to see that, in a vay, his father is alvays looking over his shoulder--'
'That's creepy.'
Sacharissa looked around the cellar. The stone walls were old and stained, but they certainly weren't blackened.
'I just saw... people. Men fighting. Flames. And... silver rain. How can it rain underground?'
'I do not know. That's vy I study dark light.'