"Helen and I drew back as one. For a second I thought Turgut and Selim must be aligned with some dark power, and I struggled with the temptation to grab my briefcase and Helen's arm and flee the apartment. How except through occult means could these two men, whom I'd thought of as my friends, work for a sultan long dead? Actually, all the sultans were long dead, so whichever one Turgut was referring to could not be of this world anymore. And had they been lying to us about a host of other issues?

"My confusion was cut short by Helen's voice. She leaned forward, pale, her eyes large, but her question was a calm one, and eminently practical, in the situation - so practical at first that it took me a moment to understand it. 'Professor Bora,' she said slowly, 'how old are you?'

"He smiled at her. 'Ah, my dear madam, if you are asking whether I am five hundred years old, the answer is - fortunately - no. I work for the Majestic and Splendid Refuge of the World, Sultan Mehmed II, but I never had the incomparable honor of meeting him.'

"'Then what on earth are you trying to tell us?' I burst out. "Turgut smiled again and Selim nodded kindly at me. 'I had not intended to tell you this at all,' Turgut said. 'However, you have given to us your trust in many things, and because you ask this so perceptive question, my friend, we will explain. I was born in the normal way in 1911 and I hope to die in the normal way in my bed in - oh, about 1985.' He chuckled. 'However, my family members always live a long, long time, so I shall be cursed with sitting on this divan when I am too old to be respectable.' He put an arm around Mrs. Bora's shoulders. 'Mr. Aksoy is also of the age you see him here. There is nothing so strange about us. What we will tell you, which is the deepest secret I could entrust to anyone, and which you must keep secret no matter what may happen, is that we are part of the Crescent Guard of the Sultan.'

"'I don't think I have ever heard of them,' Helen said, frowning.

"'No, Madam Professor, you have not.' Turgut glanced at Selim, who sat listening patiently, obviously trying to follow our conversation, his green eyes quiet as a pond. 'We believe that no one has heard of us except our members.

We were formed as a secret guard from among the most elite corps of the Janissaries.'

"I remembered, suddenly, those stony, bright-eyed young faces I'd seen in the paintings from the Topkapi Saray, their solid ranks grouped near the sultan's throne, near enough to spring on a potential assassin - or on anyone, for that matter, who suddenly fell from the sultan's favor.

"Turgut seemed to read my thoughts, for he nodded. 'You have heard of the Janissaries, I see. Well, my fellows, in 1477, Mehmed the Magnificent and Glorious called to him twenty officers who were the most trustworthy and the best educated of all his corps, and conferred on them in secret the new symbol of the Crescent Guard. They were given one purpose, which they were to fulfill - at the cost of their lives, if necessary. That purpose was to keep the Order of the Dragon from bringing any more torment to our great empire, and to hunt down and kill its members wherever they could be found.'

"Helen and I both inhaled, but for once I got there before she did. 'The Crescent Guard was formed in 1477 - the year the monks came to Istanbul!' I tried to puzzle it out as I spoke. 'But the Order of the Dragon was founded long before that - by the Emperor Sigismund in 1400, right?'

"'It was 1408, to be exact, my friend. Of course. By 1477 the Sultans had already had quite a problem with the Order of the Dragon and its wars on the Empire. But in 1477, His Gloriousness the Refuge of the World decided that there might be even worse raids from the Order of the Dragon in the future.'

"'What do you mean?' Helen's hand was motionless in mine, and cold. "'Even our charter does not say this directly,' Turgut admitted, 'but I am certain it is no coincidence that the sultan founded the Guard only months after the death of Vlad Tepes.' He put his hands together, as if in prayer -  although, I remembered, his ancestors would have prayed prostrate, on their faces. 'The charter says that His Magnificence founded the Crescent Guard to pursue the Order of the Dragon, most despised enemies of his majestic empire, through all time and space, over land and sea and even across death.' "Turgut leaned forward, his eyes glowing and his silver mane springing up wildly. 'It is my theory that His Gloriousness had a sense, or even knowledge, of the danger Vlad Dracula might deliver to the Empire after his - Dracula's -  death.' He raked his hair back. 'As we have seen, the sultan also founded at that time his collection of documents about the Order of the Dragon - the archive was not a secret, but it was used in secret by our members and still is. And now, this marvelous letter Selim has found, and your folk song, madam -  these are further proof that His Gloriousness had a good reason to worry.'

"My brain was still seething with questions. 'But how did you - and Mr. Aksoy - come to be part of this Guard?' "'The membership is handed down from fathers to eldest sons. Each son receives his - how is it in English? - his induction at the age of nineteen. If a father has only unworthy sons, or none, he lets the secret die with him.' Turgut retrieved, finally, his deserted coffee cup, and Mrs. Bora moved to fill it for him. 'The Crescent Guard was kept so well a secret that even the other Janissaries did not know that some of their ranks belonged to such a group. Our beloved fatih died in 1481, but his Guard continued. The Janissaries rose to great power sometimes, under weaker sultans, but we kept our secret. When the Empire finally vanished even from Istanbul, no one knew about us and we remained. Our charter was kept safe by Selim Aksoy's father during the first Great War, and by Selim during the last one. He retains it now, in a secret place that is our tradition.' Turgut drew a breath and took a grateful gulp of his coffee.

"'I thought,' Helen put in a little suspiciously, 'that you said your father was Italian. How did he come to be in the Crescent Guard?'

"'Yes, madam.' Turgut nodded over his cup. 'My maternal grandfather, actually, was a very active member of the Guard and he could not endure for the line to die with him, but he had only a daughter. When he saw that the Empire would end forever in his lifetime - '

"'Your mother!' Helen exclaimed.

"'Yes, my dear.' Turgut's smile was wistful. 'You are not the only one here who can claim a remarkable mother. As I think I told you, she was one of the best-educated women of her time in our country - one of the only splendidly educated ones, actually - and my grandfather spared nothing to pour into her all his knowledge and ambition, and to prepare her for service in the Guard. She became interested in engineering when that was still a new science here, and after her induction to the Guard, he allowed her to go to Rome to study - he had friends there. She was proficient in very advanced mathematics and could read in four languages, including Greek and Arabic.' He said something in Turkish to his wife and Selim, and they both nodded agreement. "She could ride as well as any cavalryman of the sultans' and - although very few people knew this - shoot like one, also.' He almost winked at Helen, and I remembered her little gun - where did she keep it, anyway? 'She learned from my grandfather a great deal about the lore of the vampire and how to protect the living from his evil strategies. Her picture is there, if you would like to see her.'

"He got up and brought it to us from a carved table in the corner, putting it very gently into Helen's hand. It was a striking image, with that marvelous delicate clarity of photographic portraits from early in the century. The lady sitting for her lengthy exposure in an Istanbul studio looked patient and composed, but her photographer, under his great black cloth, had captured something like amusement in her eyes. The sepia of her skin was flawless above her dark dress. Her face was Turgut's, but fine of nose and chin where his was heavy, opening like a crisp flower on the stem of her slender throat -  the visage of an Ottoman princess. Her hair, under an elaborate plumed hat, was piled up in dark clouds. Her eyes met mine with that glint of humor, and I regretted suddenly the years that separated us.

"Turgut took the little frame fondly into his own hand again. 'My grandfather chose with wisdom when he broke the tradition and made her a member of the Guard. It was she who found some scattered pieces of our archive in other libraries and brought them back to the collection. When I was five she killed a wolf at our summer cottage, and when I was eleven she taught me to ride and shoot. My father was devoted to her, although she frightened him with her fearlessness - he always said he had followed her back to Turkey from Rome to talk her out of too much bravery. Like the most trustworthy wives of the members of our Guard, my father knew about her membership and he worried constantly about her safety. He is over there - ' He pointed to a portrait in oils that I had noticed earlier, where it hung by the windows. The man looking out of it was a solid, comfortable, quaint person in a dark suit, with black eyes and hair and a soft expression; Turgut had told us that his father had been a historian of the Italian Renaissance, but I could easily imagine the man in the portrait playing marbles with his young son while his wife tended to the boy's more serious education.

"Helen stirred beside me, stretching her legs discreetly. 'You said your grandfather was an active member of the Crescent Guard. What does that mean? What are your activities?' "Turgut shook his head regretfully. 'That, madam fellow, I cannot tell even you two in detail. Some things must remain secret. We have told you this much because you asked - you almost guessed - and because we would like you to have complete faith in our assistance. It is very much to the benefit of the Guard that you should go into Bulgaria, and go as soon as possible. Today the Guard is small - there are only a few of us left.' He sighed. 'I, for one, alas, have no son - or daughter - to whom to pass my trust, although Mr. Aksoy is raising his nephew in our traditions. But you may believe that all the power of Ottoman determination will go with you, in one way or another.' "I resisted the urge to groan aloud again. I could have argued with Helen, perhaps, but arguing with the secret might of the Ottoman Empire was beyond me. Turgut raised a finger. 'I must give you one warning, and a very serious one, my friends. We have put into your hands a secret that has been kept with care - and with success, we believe - for five hundred years. We have no reason to think that our ancient foe knows it, although he surely hates and fears our city as he did in his lifetime. In the charter of the Guard, His Magnificence laid down his rule. Anyone who betrays the secret of the Guard to our enemies will be punished by immediate execution. This has never occurred, to my knowledge. But I ask you to be careful, for your own sakes as well as ours.'

"There was no hint of malice or threat in his voice, only a grave depth, and I heard in it the implacable loyalty that had made his sultan conqueror of the Great City, the previously impregnable, arrogant city of the Byzantines. When he had said, 'We work for the sultan,' he had meant exactly that, even if he himself had been born half a millennium after Mehmed's death. The sun was sinking lower outside the parlor windows, and a rosy light reached Turgut's big face, suddenly ennobling it. I thought for a moment how fascinated Rossi would have been by Turgut, how he would have seen in him living history, and I wondered what questions - questions I could not even begin to formulate myself - Rossi might have asked him.

"It was Helen, however, who said the right thing. Rising to her feet so that we all rose with her, she gave her hand to Turgut. 'We are honored by what you have told us,' she said, looking proudly into his face. 'We will guard your secret and the wishes of the sultan with our lives.' Turgut kissed her hand, clearly moved, and Selim Aksoy bowed to her. There seemed no need for me to add anything; setting aside for the moment her people's traditional hatred of their Ottoman oppressors, she had spoken for both of us.

"'We might have stood that way all day, looking wordlessly at one another as the twilight fell, if Turgut's telephone had not suddenly given a screech. He bowed his excuses and went across the room to answer it, and Mrs. Bora began to load the remains of our meal onto a brass tray. Turgut listened to his caller for a few minutes, spoke in some agitation, and then replaced the receiver abruptly. He turned to Selim and addressed him in rapid Turkish, and Selim quickly put on his shabby jacket.

"'Has something happened?' I asked.

"'Yes, alas.' Turgut smote his chest with a punishing hand. 'It is the librarian, Mr. Erozan. The man I left to watch him went out for a moment, and he called now to say that my friend has been attacked again. Erozan is unconscious and the man is going for a doctor. This is very serious. It is the third attack, and just at sunset.'

"Shocked, I reached for my jacket, too, and Helen slipped on her shoes, although Mrs. Bora put a pleading hand on her arm. Turgut kissed his wife, and as we hurried out, I turned once to see her standing pale and frightened at the door to the apartment."