"Perhaps half an hour."

Niall burst out laughing. "That's all right. I can wait that long. I'll go to the dining room. Would you give me a call when you're ready?"

The dining room was on the same floor as the "Florentine" gallery. It was a small room, containing no more than a dozen tables, although since Niall had been eating there regularly, these had been enlivened with attractive table cloths, and the food was served on decorated china plates instead of plastic dishes. There was no fresh food available, but the food synthesizer was of such a high standard that its products were greatly superior to the food cooked by Niall's own kitchen staff. Even after six months he was still astonished by its variety.

The synthesizer was an oblong metal box, about three feet long, which was attached to the wall beside the window. The menu that was displayed above it offered a list of food and drink amounting to more than a hundred items, beginning with hamburgers (with or without onions) and ending with Burgundy, Bordeaux, and American Chardonnay. Over the past six months Niall had sampled everything on it, from pate de foie gras and tournedos Rossini to peach melba and crepes suzettes; he had finally concluded that his taste was too unsophisticated for most of these culinary marvels, and that he preferred a two-course meal of fish and chips and pecan pie with pistachio ice cream. This is what he now proceeded to order from the synthesizer, unaware that in so doing he was merely confirming the verdict of dozens of generations of teenagers. He also ordered a glass of sparkling apple juice, whose taste he greatly preferred to that of wine.

As he ate he looked out the open window at the bustling market scene, which looked exactly as it must have looked in the days of Lorenzo de'Medici. Niall had come to recognize many of the stallholders and their typical cries, as well as many of the servants and housewives who made regular visits to the market. The man who ran the butcher's stall on the corner had a hoarse shout that could be heard above all the other sounds of the city, including the bellowing of cattle and the bleating of sheep. Like most of the males in the square, he took a keen interest in the red-haired peasant woman who ran the vegetable stall that was directly opposite Niall's window. This woman, who was in her mid-thirties, was taller than the average man, and had a magnificent ringing laugh and a jaunty way of throwing back her head and placing her hands on her hips. She made Niall think of a noisier and coarser Princess Merlew. Most of the men enjoyed laughing and joking with her, and although Niall was unable to understand the language, he guessed from the ribald laughter that many of the jokes must have been indecent.

She was also the object of admiration of a wealthy young man who stopped at her stall at least once a day -- he wore a purple doublet, a hat that reminded Niall of an inverted flower bowl, and rode a chestnut mare. This young man was regarded with dislike and derision by the male stallholders, particularly the butcher; but Niall sensed that their hostility was based on envy, and on a certain fear that the redhead would one day surrender her virtue to the lovesick gallant. Niall entertained the same suspicion; one day toward evening, when most of the stallholders had packed up and left, he had seen the young man present her with a bouquet of flowers, and -- after glancing around to see that no one was watching -- the woman had accepted them and hidden them under her stall. But when he leaned forward and whispered something in her ear, she had shaken her head vigorously. And the butcher, who had come out from behind his stall at that moment, had scowled angrily, and as the young man rode away, he spat on the ground.

Now, as Niall gazed out of the window, he witnessed an interesting scene between the red-haired woman and a boatman who had moored his craft by the first flight of steps that ran up from the river to the market square. The boatman was carrying a large fish -- it must have been more than a foot long -- and was obviously trying to persuade her to buy it. She shook her head, as if objecting that he was asking too much. He leaned forward and said something; she looked thoughtful, then finally nodded her head and handed over money and a basket of a green vegetable not unlike cabbage. The man went behind the stall and placed the fish in a box. Then, as he was turning away, he took the woman's arm and pulled her toward him. Niall could not see what happened next -- the man's body was between them -- but the woman's reaction was to give him a box on the ear that made him stagger. The woman on the next stall began to laugh loudly -- she had a most unpleasant cackle -- and this seemed to enrage the man, who tried to take back his fish. The woman grabbed the box and held it out of his reach. Within a few seconds there was a noisy quarrel involving at least half a dozen men and two women, as well as a half- starved mongrel, which barked furiously and tried to bite the fisherman's leg. The man quickly got the worst of it -- he had clearly expected to be allowed certain liberties in exchange for selling the fish cheaply -- and he slunk off to his boat, leaving the basket of vegetables behind. And the stallholders, obviously sorry that the diversion was over, went reluctantly back to work. The overexcited dog went on barking until a man gave it a kick that lifted it off the ground; it vanished toward the river with a pathetic yelp.

Niall had been watching all this with such total absorption that he jumped in alarm when the old man's voice spoke in his ear. "I am sorry I have taken so long. The task was more complicated than I expected."

"It doesn't matter. I've been watching that woman down there." He was struck by a sudden suspicion. "Or did you arrange it all to keep me amused?"

"No. Today is market day. If you had been here yesterday the square would have been empty." He pulled up a chair and sat down on the other side of the table. Since he was unreal, this pantomime was unnecessary; yet, as he had often explained to Niall, the crowning achievement of the Steegmaster was the extraordinary detail of its realism.

Niall spooned up his melted ice cream. "Did those people down there really exist?"

The old man looked at him with mild reproof. "Since the camera was not invented in 1490, that is obviously an impossibility."

Niall looked down at the red-haired woman, who was now showing off her fish to the woman on the next stall.

"So if I was a magician, and I could travel back to 1490, these people wouldn't be there?"

The old man sighed. "What you call time travel is a verbal misunderstanding.

Time is merely another name for process. In theory, process can be reversed, but to restore the universe to its state of five minutes ago would take an infinite amount of energy. Therefore, to travel into the past would be quite impossible."

Niall asked: "And is that also true of the future?"

"Not quite. Anyone can predict the future. I can tell you the exact time the sun will rise tomorrow. I can even tell you what the weather will be like. Yet I am not a magician."

Niall said: "I dreamed of the future last night, and when I woke up, it happened exactly as I dreamed it. Does that mean I am a magician?"

The old man shrugged. "I am not programmed to answer that question." Then, oblivious to Niall's grimace of frustration, he went on: "Do you wish to hear what I learned about the nature of magic?"

Niall sighed. "Very well."

"I admit that I was mistaken to believe that it was merely an irrational superstition." Niall looked up with renewed interest. "It appears to be an oddly consistent system of belief, whose foundations cannot be clearly distinguished from those of religion."

Niall frowned; he always found abstract jargon difficult to absorb.

"I see."

"As far as I can see, it appears to be based upon a number of propositions. The best known of these is attributed to the legendary founder of magic, Hermes Trismegistos, and it states: 'As above, so below.' This appears to mean that every man is a miniature version of the whole universe. "

Niall tried to look as if he understood.

The old man went on: "But according to magical philosophy, the universe does not consist of dead matter -- in fact, there is no such thing as dead matter. Everything in the universe is alive."

Niall said: "Like that stone figure I tried to bring into the tower?"

"Possibly." The tone was noncommittal. "The magical view is that all matter exists outside space and time, in a multidimensional universe. We only see one small aspect of a being that reaches back through many invisible planes of existence. It follows, of course, that human beings also exist on many planes of existence, although they are not aware of it. According to the Cabalists, there are ten planes of existence, the highest being God and the lowest earth. In human beings, these planes of existence are planes of consciousness. Am I going too fast for you?"

"No." This last comment had aroused Niall's attention. "So there are ten planes of consciousness?"

"According to the Cabala."

"Are you saying that if you could get up to a higher plane, you'd be a magician?"

"That appears to be the position."

Niall shook his head and sighed. "I don't follow that. If I can rise to a higher level of consciousness, surely the only person it affects is me? It's like getting drunk. When I've had a few glasses of mead, everyone seems much nicer. But they haven't really changed -- it's just me."

"A perceptive comment. But according to magical philosophy, the best way to change the world is to change your own consciousness. One alchemist wrote: 'Magic is the art of causing changes in consciousness at will.' According to the same writer, luck is an example of the use of magic. When you feel lucky, you usually are lucky. You somehow make lucky things happen to you. And people who feel unlucky seem to make unlucky things happen to them. According to another alchemist, this is the real meaning of 'As above, so below.' Everyone knows that the mind can be affected by the external world -- that a dull day can make you feel dull. But the magician is someone who knows that the mind can also affect the external world. When you are full of courage and optimism, you somehow make good things happen to you."

Niall shook his head in wonderment. "And that's magic?"

"According to the books I have consulted."

Niall said thoughtfully: "This magician doesn't seem to have been very lucky."

"I beg your pardon?"

"This man who sent Skorbo's killers. First two of his servants get carried off by Skorbo. And when they've killed Skorbo they all get caught. That doesn't sound very lucky, does it?"

The old man's face remained inscrutable, an indication that he failed to grasp what Niall was talking about. "No doubt you are correct."

Niall said thoughtfully: "So it sounds as if it's my luck against his."

This time the old man made no comment. After a long silence he said: "Do you wish me to continue to summarize the nature of magic?"

Niall shook his head. "Not now, thank you. But I'd like to ask your opinion about that dream. Do you know about the girl we found hanging upside down in Skorbo's larder?"

"Yes." The Steegmaster's ability to read thoughts meant that it was able to perceive every important event that occurred in the city.

"I dreamed about her last night. I dreamt that Simeon came and cut off her tunic with a big pair of scissors, and I saw that she had bits of brown stuff, like dead leaves, stuck to her skin. Well, when I woke up, Simeon did cut off her tunic with a pair of scissors, and she did have bits of brown stuff stuck to her skin. How can you explain that?"

"And were they dead leaves?"

"No. They were this stuff." He bent down and picked up the flat box from under his chair. "Seaweed."

The old man took a damp brown frond between his thumb and forefinger, and stared at it intently. Niall knew enough of the operations of the Steegmaster to know that it was being chemically analyzed.

"This is not seaweed."

"It's not?" Niall was astonished. "It smells like it."

"Sea water contains a precise percentage of magnesium, sulfur, and calcium, as well as fifty-eight other elements. This contains far too much of all three, as well as a high percentage of phosphorus. That indicates that it comes from a freshwater lake with a high mineral content. It could be the crater of an extinct volcano."

"Could it be an underground lake?"

"Impossible. Even weed requires light to grow. As you can see, this weed was not originally brown but green." He placed his finger on a small area of weed that was, in fact, a pale green. "It has oxidized to this brown color."

Niall stared at the brown mat of weed, whose smell filled the room.

"And that means sunlight?" "Of course. Plants live by photosynthesis -- absorbing carbon dioxide to produce sugar."

"Have you any idea where it might have come from?"

"I cannot be specific. There are a dozen extinct volcanoes within fifty miles."

Niall recalled from his sleep-learning sessions that the approach of the comet Opik had produced many volcanic eruptions.

"And are there many lakes with that kind of high mineral content?"

"Certainly not in this region."

"Could it be identified?"

"Unfortunately, I know of no such lake. But you must remember that most of my geological information dates back several centuries."

Niall lifted the mat of weed, and held it up by its corners. "Why do you suppose the magician's servants brought this with them?"

A silence of ten seconds indicated that the Steegmaster was surveying many alternatives. "Possibly it has some religious significance."

"Religious?" This idea bewildered him.

"Or it may have been used in some kind of magical ritual."

"What kind of ritual?"

"That is impossible to say. There was a tribe of Indians in Ecuador who wore a garment made of leaves from a sacred tree for their magical ceremonies. You observe that this mat is a human artifact."

This also came as a surprise. Niall spread out the weed on the tabletop. Now that he examined it closely, he could see that the old man was correct. A number of pieces of weed had been woven together so skillfully that it was virtually impossible to see the joins. He held it out at arm's length. Yet it was obviously a mat, not some kind of a garment. He sighed with exasperation as he refolded it and replaced it in the box.

"They must have had some reason for bringing it. But what could it have been?"

"I can offer no other suggestions."

Niall looked out the window at the sunlit market scene, which was now busier than ever. "And if time travel is impossible, how did I dream of the future. Can your books on magic explain that?"

"Magical philosophy states that the mind exists outside space and time. Only the body is subject to these limitations. So when the body is asleep, the mind may be able to pass beyond space and time."

Niall asked with excitement: "Do you think that's true?"

The old man smiled gently. "How could I?" Niall shrugged impatiently. "I have no means of judging whether such a theory is true or not. I exist merely in space and time. You are alive, which means that you are not entirely limited by space and time. You must judge for yourself."

Niall felt a twinge of remorse. "I'm sorry." He stood up. "And thank you for your help." Apologizing made him feel calmer, less frustrated.

"It is always available." His courtesy made Niall feel even more ashamed of his impatience.

The position of the sun in the sky showed that it was about two hours after midday. As he moved from behind the table, Niall became aware of the box in his pocket.

He had totally forgotten about it. "Have you any idea what this is?" The old man took the pointed quill and held it in the palm of his hand.

"Yes. This is a primitive form of hypodermic syringe, of the kind invented in the seventeenth century." He uncorked the bottle and sniffed its contents. After a pause he said: "And this is human blood serum containing traces of spider venom."

Niall snapped his fingers. "Of course! I should have guessed! A serum against the poison of the death spiders. Do you think it will work?"

The old man shook his head. "There is only one way to find out -- by experiment."

"Thank you." Niall was already halfway to the door when the old man stopped him.

"You have forgotten your lakeweed. Where are you going in such a hurry?"

"To the hospital. It's full of people who've been paralyzed by spider venom."

"In that case, they will still be there when you arrive, will they not? Remember that impatience is the worst of human failings." But Niall was already out of the room.

As he approached the hospital, Niall saw that the main doorway was blocked by a small crowd. The hall beyond was also full of people, and a babe in arms was crying lustily. Niall made his way round to the rear entrance, and was relieved to find it deserted. The first person he saw when he stepped inside was Phelim.

"What's happening?"

"Word got around and they've all come looking for relatives."

At the far end of the corridor, three nurses were forming a human barrier to hold back the crowd, and a powerfully built woman, whom Niall recognized as the matron, was admonishing everyone to make less noise. The door of the room in which the unconscious bodies were laid out stood open. As they approached, a woman rushed out, her hands over her face, wailing noisily. Behind her, Simeon was shaking his head with angry disgust.

"Damn fool! She wants to take her husband back home. I told her he'd be better here." He noticed Niall, and made an obvious effort to regain his equanimity. "Hello, my boy. You can see what chaos we're in."

Half a dozen people were wandering around among the prostrate bodies, peering anxiously into unconscious faces. One of them, a dark-haired girl in a simple yellow dress, seemed vaguely familiar.

Boyd came into the room, carrying an oblong metal container, with a large and badly worn book balanced on top of it. He was obviously pleased with himself. "Look what I've found."

Phelim said resignedly: "Go on. What is it?"

"An ECT apparatus."

Simeon said: "A what?"

"Electro-convulsive therapy. Look, here's a piece about it." He opened the book and handed it to Simeon, who fumbled in his pocket and took out a pair of gold-rimmed spectacles, which he balanced on his nose.