"We spoke, in particular, of Julius Caesar," said Father Peabody, rubbing his hands on the front of his long black cassock. "There is a man whose greatness is not in dispute, I venture to claim." He spoke with a broad flat local accent, and bobbed his head humbly after every other word as though overconscious of his inferior social status. "Well, as to Caesar," said Don Miguel, a little more snappishly than he had intended because he was so irritated at being sent for on such a petty excuse, "I can give you accurate information. As it happens, I've spoken to him. I found him to be a perfumed fop. In his youth, he was guilty of abominations with men, and in his maturity his promiscuous behaviour was such that the gossip of all Rome centred on it. If this was greatness in his private life, you may maintain so; I would not." Don Marco flushed and drew back half a pace, with a sidelong glance aI the Marquesa. "It does not seem fitting to speak of such matters in the hearing of a lady!" he exclaimed. "Kindly refrain from blaming me -- blame rather Caesar himself," Don Miguel answered frigidly. "Her ladyship asked my expert opinion, and I've given it. History is an impartial force, Don Marco; it has no patience with those dabblers who prefer to turn aside from what displeases them, and it's full of unpleasant but inescapable facts." Don Marco's flush deepened still further, and -- after a moment's debate with herself -- the Marquesa gave an emphatic nod. "Indeed, Don Marco, Don Miguel is perfectly correct to say this. It is the fruit of a false prejudice which has led to us women being sheltered and pampered and, not to mince words, lied to about the nature of the world! It suits the interests of overweening men to invest us with a weakness we don't possess!" She raised her sharp eyes to Don Miguel's face, and heaved a sigh. "But that we have in our midst a man who has spoken with Caesar! Is it not miraculous?" "We of the Society of Time do not regard it as such," Don Miguel answered, already regretting that he had made his little boast. "It's an application of natural laws, nothing more. A miracle, perhaps, would be to discover a means of flying to the moon. No one has yet suggested how that might be accomplished." "With -- with respect, Don Miguel!" said Father Peabody, bobbing his round head in which his eyes were even rounder. "How was it possible for you to talk with Caesar? I understood, if you will pardon me, that the rules of your Society forbid interference and limit the activity of time-travellers to simple observation!" I knew I shouldn't have opened my mouth in this kind of company . . . The thought flickered across Don Miguel's mind and left a trail of self-directed irritation. But it was too late now to do other than answer the clerics sharp question. Anyway, the published data on the Society's investigation of Rome themselves implied how the trick was worked, and a truly astute man would not have needed to inquire. He said wearily, "I assure you, Father, the rules are most strictly adhered to. It does not, however, constitute interference if a notable historical personage utters words he would have uttered anyway in the hearing of a person he does not know and will naturally never meet again. Does that make the method clear?" Father Peabody gave a succession of vigorous nods, and there was a short silence. The Marquesa broke it at last. "I may be only a poor stupid woman," she said, and paused as though waiting for automatic contradiction. Not getting it, she shot a venomous glare at Father Peabody, but was forced to continue. "To me," she resumed, "it seems that interference with the past is out of the question. What was, was! How can it be changed by our intervention?" Don Miguel repressed a desire to scowl even more fiercely than she had just done. For all her vaulted intellectual accomplishments, the Marquesa had framed a question which no fifteen-year-old schoolboy of average intelligence would have wasted breath on. He would have been taught the answer in class, or pieced it together himself from items in the news. Indeed, even Don Marco -- who did not strike Don Miguel as exceptionally bright -- showed visible surprise at hearing it. "The basic arguments, my lady," Don Miguel said reluctantly, "are rather a matter for speculative philosophers than for a pragmatic person like myself. But I have some conception of them, and if you wish I'll try and elucidate." A shadow of discomfort, as though caused by the realisation that she had let herself in for some heavy brainwork, crossed the Marquesa's face. But she composed herself and adopted an expression of polite interest. "Do so, if you will," she murmured. "Very well." Don Miguel hesitated, trying to cast his thoughts into words suitable for her. "To begin with, there are, are there not, in history certain crucial turning-points? Yet each of these in turn was composed of the sum of vast numbers of individual acts and attitudes, and it's rare that we can fine down any event in history to the point of being able to attribute it to one unique causative factor. The maiority stem from such a wide spectrum of influences that we cannot grasp the entire range -- effectively, therefore, we must regard them as random. The fall of Rome, for instance, was not only due to the invasion of a barbarian horde; it was also due to decadence among the Romans which prevented them from offering much resistance." The Marquesa nodded. She was beginning to frown, but Don Miguel continued on the assumption that she was not yet out of her depth. "This vast flow, or stream, of events tending towards a crisis might be compared, in one sense, to a river. The presence or absence of a single pebble on the river's bed will make no significant difference to the course of the waters, and no detectable difference to the level along the bank. Detectable or not, however, it is a difference -- a priori! Therefore one may also compare the time-flow to an avalanche. It is not beyond the bounds of possibility that something done by a visitor from the future might serve to stay the first stone that triggered the landslide, and thus turn history into another course. If that happened, we might rule ourselves out of existence! One key idea planted in the mind of a Roman of the year 300 might, for all we are able to predict, result in the defeat of Alaric and the survival of the Roman Empire!" "I'm fascinated by the great empires of the past!" said the Marquesa with enthusiasm. "Especially by -- " She noted the look of annoyance on Don Miguel's face, and broke off. "I was carried away," she concluded apologetically. "Do go on!" "You've followed me so far?" Don Miguel countered. "Ye-es . . . Except that if something we did were to change history, how would history have been changed? I mean, without us having gone back to change it?" With great effort, Don Miguel said patiently, "The question simply wouldn't arise! This would be history. It would be all the history there was." Father Peabody shook his head, a look of resigned wonder on his face. "Truly the ways of the Lord are inscrutable!" he said. The Marquesa gave a sudden nod and smile. "I see!" she said, and then added doubtfully, "I think . . ." Don Marco spoke up. "Are there not, though, crisis points in history where regardless of what we were or were not to do the outcome would be little affected?" "Oh, certainly," agreed Don Miguel. "The classic example, of course, is one which we all know -- the storm which broke the English defences four hundred years ago, doused their fireships, and in effect made certain the conquest of Britain. Men could hardly interfere with the brewing of a storm! Even in cases such as that, however, it's imperative to be very, very discreet." "Oh, surely the result was a foregone conclusion in any case!" objected the Marquesa. "I mean, the Armada was so huge and so well-armed . . ." "I can assure you, my lady, we have studied the matter exhaustively. The most eminent strategists and naval authorities agree that encumbered as they were with occupation troops and supplies the galleons might well have been worsted -- especially if the English fireships had got among them with a steady following wind. No, it's well established that it was the fortunate coincidence of the storm breaking which tipped the scales of battle to our side." "I think I follow," said Don Marco, frowning. "What must not under any circumstances be done in such an instance, therefore, is to -- well, to cause a delay in the arrival of the fleet, so that the storm has already blown over. Am I right?" "Yes, precisely so." "To think that we hang by such a thread!" marvelled Father Peabody aloud. It would have suited Don Miguel to perfection if at this point he had been able to snap the thread tying him to the Marquesa; however, she was determined not to let that happen yet. Stretching out one heavily beringed hand to touch his arm, she said, "Now there's something else, Don Miguel, which I must take this opportunity of asking you. I've heard that in this quatrocentennial year your Society has permitted certain especially favoured outsiders to witness the actual victory -- is this so?" "No, of course it's not!" Don Miguel was genuinely shocked. "From whom did you hear such nonsense? The rules of the Society are absolutely inflexible: only Licentiates are permitted to travel beck in time. The purpose of time-travel is serious historical research; it's not a -- a carnival, a spectacle for sensation-seekers!" "Curious," mused the Marquesa. "I had been assured . . . But no matter! Yet I find it in my heart to wish the rule was not so rigid. I have such a burning desire to assist at some great happening of the past." "We have brought back pictures -- " began Don Miguel. "Ah, pictures! Pictures are flat and lifeless! What are pictures beside a view of reality? But your heart is hard, Don Miguel. I see that." "My lady, time-travel is far from a pleasure trip. The dirt, the squalor, the cruelty, the -- the disgusting facts of life in earlier ages, in short, account for that." "Ah, but dirt and squalor are still with us. Why, yonder in the market outside the city wall of Jorque itself, them are people infested with lice, who probably don't know the meaning of the word soap! I have no desire to view their ancestors -- they were doubtless the same fifty generations ago. But I would greatly love to see the splendours of the past. As I began to say earlier" -- she punctuated the sentence with an arch look of reproach that belonged in the armoury of a far younger woman -- "I am most fascinated by the empires of bygone days. The empire of Mexico, for instance, with its wonderful goldwork and featherwork!" "And its pleasant custom of sacrificing human beings by tearing out the living heart and displaying it to the victim," sourly responded Don Miguel. "Have you no romance in you?" cried the Marquesa. "It is not I that lack romance; it is the empire of the past you so admire." "And yet . . ." She let the words trail away and gave a delicate, lady-like shrug. "Well, I confess I called for your expert opinion, and since you've given it I cannot do otherwise than accept what you tell me. Nonetheless, let me at least show you on what grounds I base my admiration. I have a new treasure, a golden mask of Aztec manufacture -- I'd like to show it off to you and see if I cannot persuade you that there were some fine things in the olden days." "If you're seeking my expert opinion on that also, I'm afraid I can't oblige you," Don Miguel countered. "I know little of goldwork or jewellery." "Ah, but no one could fail to be impressed by my great mask! Come!" She clapped her hands, and the tall Guinea-man who attended on her hurried to clear them a way through the throng. III "I trust you will not think it brazen of me," said the Marquesa, "when I tell you it's in my bedchamber that I've hung the mask. I feel it's an insult to the dignity of women to assume they cannot protect their own virtue if they happen to be in the same room as both a man and a bed." By this time she had practically succeeded in making the enlightened and progressive Don Miguel into a conservative bigot; accordingly he retorted, "You must admit it's equally an insult to us men, my lady, if you assume we are inevitably inclined to make improper advances." The Marquesa's lips tightened to a thin white line; then she forced herself to relax. "True, true! One who pleads for equality between the sexes cannot do other than agree." But she looked extremely unhappy at having to do so. In the wake of the Guinea-man they left the crowded reception hall and passed along a corridor where their footsteps echoed on magnificent Moorish tiling, until they came to a room whose door their accompanying slave opened with a key from a chain at his waist. The interior was large and luxurious, dominated by a great bed disguised as a bank of green moss. The walls and ceilings were festooned with the Marquesa's beloved creepers, and an adjacent bathroom was revealed through a half-curtained gap on the far side. But after the first glance Don Miguel saw nothing more of the room. His whole attention was riveted by the gleaming mask mounted on the wall facing the foot of the bed. Hardly daring to breathe, he walked over and stood gazing at it. It was indeed, as the Marquesa claimed, magnificent. And it was more than merely a mask. It was a representation in beaten gold of the head-dress, face and shoulder-plates of an Aztec warrior. The square, snarling face was nine inches deep, the head-dress was twice as high, and the shoulder-plates were a good fifteen inches on each side. It nearly dizzied him with its rich yellow lustre. "Ah, you're capable of being impressed after all!" exclaimed the Marquesa. "I'd begun to imagine you lacked all traces of emotion! Am I not justified in feeling proud of it?" Don Miguel put out his hand to touch the thing, half hoping it would prove to be a mere illusion. But the heavy metal was solid and cool to his fingers. He stepped hack, his mind in a whirl as he noted the signs of genuine Aztec workmanship the mask bore.