"Sorry again," she said. "I didn't know that. Most people don't have a clue about the damage you can do to old parchment just by touching it with your bare fingers."

Mallory silently lifted his gloved hands in front of her face, and she nodded.

"I'll need to get some professional advice myself on how best to preserve it," she said.

"So I presume you've copied it?" he asked, sounding only slightly mollified.

"I've copied it and scanned it as well. That was pretty much the first thing I did after I got over the shock of the booby trap triggering."

She lifted the parchment carefully, using a couple of pencils, lowered it into the book safe, and then closed the lid, pressing it down until the catch clicked to lock it. Then she carried it over to the safe from which she had removed it a few minutes earlier, put it inside, and locked the door.

"Do you think it's valuable?" Mallory asked. "That book safe, I mean."

"I really don't know. When I realized what it was, I assumed it was just a curio, and there are people who collect that kind of thing-medieval instruments and weapons and so on-but I really have no idea if this has a significant value or not." She laughed shortly. "The reason I'm keeping it in the safe is so that I don't stab myself with it and nor does anybody else who comes up here, like Betty."

"Betty?"

"The lady who runs the shop for me. I'll introduce you later. I can just see her wandering up here to ask me something and pricking the end of her finger on one of those spikes. But now that we've looked at it more closely, I'm beginning to think that it might well be valuable, simply because I've never seen anything like it before. I've done some searches on the Internet, and although book safes aren't unknown, I can't find any mention of medieval ones, and I couldn't find any that contained any kind of built-in antitheft device. Often in those days, important books included a lock of some sort to prevent them from being opened, but they were still just books, not safes, so I suppose it could even be unique. I'm still convinced it's medieval, and it's in pretty good condition, and rarity, condition, and age are all ticks in the right boxes as far as serious collectors are concerned."

Mallory nodded. "It's an impressive piece of kit and if you want my opinion-and I suppose that's the reason I'm here right now-without even taking a look at the parchment, I can tell you that whatever it is and says is important. Or at least it was important when it was put inside that relic, which isn't quite the same thing. Nobody would go to this kind of trouble, to have an object like that made, unless the contents were crucial to them in some way. So I guess the next step is to take a look at the text on the parchment and try and find out what it says."

Robin sat down in the swivel chair and pulled open one of the drawers. She took two sheets of paper out of the drawer and slid them across toward Mallory.

"You'll recognize the first few words because those were the ones I sent you," she said.

Mallory nodded, opened his computer case, and took out a sheet of paper on which he'd written the alphabet and the left-shifted Atbash cipher.

"This should be easy enough," he said.

But Robin shook her head decisively. "Not necessarily. After we talked and I read your e-mail, I wrote out the cipher as well, but when I tried it on another section of text, all that happened was I turned gibberish into a different kind of gibberish, but certainly not into Latin or any other language that I recognized."

"Did you, now?" Mallory said, looking down thoughtfully at the photocopy on the paper in front of him. "Well, I think that's good, because I like a challenge. It sounds as if whoever wrote this might have used more than one encryption technique, and that's interesting in itself, because again it suggests that whatever this text says it is-or at least it was when it was written-extremely important to somebody."

Mallory looked at the photocopy again, then shook his head.

"It's not that easy to read even in the original," he pointed out. "In some places I can't really see where one word begins or ends."

"A lot of medieval documents were like that," Robin replied. "Paper was a fairly rare and expensive commodity, so the words were crammed together and the whole width of the paper was used. And of course parchment was a lot more expensive than paper."

"Well, we need to get this right, without any mistakes, just in case this reveals the location of the lost treasure of King John or something like that."

"Not very likely," Robin said, with a smile. "So, what do you suggest?"

"I know it will take a lot longer, but I think the first thing we should do is transcribe the whole of the original text onto a computer, letter by letter. That way we'll be able to identify any ambiguous letters and play around with the spacing if we aren't sure where one word ends and the next begins. Then we can print it out because it'll be easier to write the deciphered Latin text underneath, and an English translation under that, in the old-fashioned way, using paper and ink."

"Okay. It'll take a while, but that's not a bad idea. I'm more used to looking at this kind of material than you are, so let me suggest that I read out the letters from the photocopy, while you type them."

Mallory nodded.

"That works for me," he said.

He opened his computer bag again, took out his laptop, and switched it on. He started up his word processing program and created a new file named "parchment.docx," then waited with his hands poised above the keyboard.

Robin removed her spectacles and placed them on her desk, then picked up a pencil.

"You can read without glasses?" Mallory asked.

She nodded. "Yes. They're plain glass, not prescription lenses, more a kind of disguise. I find I get taken a lot more seriously if I wear glasses than if I don't. I know I'm not blond, but I've more or less seen the word bimbo forming in the minds of some men-people like my first bank manager here in Dartmouth, for example-when I've been trying to discuss business with them. So now I tend to wear them most of the time when I'm out and about, but actually my vision's pretty near perfect."

Mallory considered her for a moment.

"I get the feeling there's an awful lot about you that I don't know yet," he said.

"You have no idea," Robin replied, "but I would remind you that you're the one who won't talk about that scar on your cheek."

"Touche. Maybe later. Right, let's get started."

Robin began reading out the individual letters that formed the text of the medieval parchment, drawing a neat diagonal line through each one as she did so. Where the letter was in any way ambiguous-sometimes the letter O, for example, could look like a Q, or C resemble a G-she drew a circle around the letter and told Mallory to put both the possible letters in brackets for the decryption that would follow.

She also told him to put a space after every letter that appeared to be the last one in a particular word. She was fairly sure she wasn't always getting everything right, because Mallory's earlier comment had been accurate: in a few places the words seemed to run one into the next without any break that she could see, and the quill or whatever had been used to write the text had had a thick point, so the letters themselves were heavy and difficult to interpret. To complicate it still further, in some areas the ink had faded significantly, and the letters were even more difficult to read in consequence.

But they quickly settled into a routine as the parchment began to yield its secrets, or at least the encrypted text, in its entirety.

11.

Via di Sant' Alessio, Aventine Hill, Rome, Italy "It's not the first time this has happened," Toscanelli responded. "Are you quite certain about it?"

Vitale nodded. "We've never before had such a precise result from any of our surveillance mechanisms. This time we are positive that the relic has at last been discovered again after having been lost for so many centuries."

"Please convince me," Toscanelli said.

"The term was entered into a search engine in Britain. In fact, the user carried out quite a number of searches, most of them including the one expression we are almost certain would be used, the Latin Ipse Dixit-"

"The master's words," Toscanelli interjected.

"Exactly, but some of the searches, especially the later ones, also included words like manuscript and medieval, so it seems almost certain that the person who initiated those searches is in possession of the relic. We've printed all the search terms entered from that one location."

Vitale picked up one of the sheets of paper from the desk in front of him and passed it across.

Toscanelli glanced at it with professional interest.

"They got the title right," he said. "As far as we know, the relic bore the name Ipse Dixit, and that's not likely to be a mistake. So that looks like a confirmation that they have somehow found it. We need to move fast."

"Faster than you think. We want this sorted within hours, not days. We simply can't afford under any circumstances for the text to be decrypted, not after all the years we've been looking for it."

Toscanelli nodded.

"Where do I need to go?" he asked, "and how big a team am I taking?"

"The target is a man named Robin Jessop and he's in southwest England in a town named Dartmouth. There will be six of you in total, and the other five have already been briefed and are on their way to Ciampino Airport, where there's a private jet waiting for you. You will use your real name, and you alone will be responsible for communicating with this office. All your equipment, including weapons and the documentation you'll need, will be on the aircraft when you get there. As always, none of you are to take any personal identification with you whatsoever. This has to be a completely deniable operation. Under no circumstances are the British authorities to find out what is happening, and the usual rules will apply in the event of any of your team being compromised or apprehended."

Toscanelli nodded. "They are to be silenced, permanently, before they can be interrogated."

"Exactly. Ensure that they all know that before the operation commences. In this case, you should meet no problems. The man is a bookseller in a small coastal town in England. He will not be armed, and may well be elderly-so far, our systems have not been able to determine that. Once you have retrieved the relic, any and all evidence that he may have already deduced about it is to be either recovered and brought back here or destroyed. Fire is probably the preferred method, as it will conceal almost everything."

Vitale handed over a black-colored folder. "All the information we have is in here. The whole sequence of events, the search terms used, and of course all the address details for this man Jessop."

Toscanelli nodded again. The operation sounded simple and straightforward, and he only had one final question to which he thought he probably already knew the answer. But for the benefit of the recorders that he knew would be running in the background in the office, he needed to hear the instruction. "And Jessop himself? What about him?"

"He is to be eliminated. If possible, make it look like an accident. If not, use any method that seems expedient and effective. But it is essential that he is dead before you leave the scene."

12.

Dartmouth, Devon It took the pair of them well over an hour to transcribe the entire text of the parchment into the computer, a long, boring, and tiresome operation.

When they'd finally finished, Mallory copied the file onto a memory stick and gave it to Robin, who transferred the file onto her own laptop and printed two copies of the transcribed text on her laser. Then she handed back the memory stick, stood up from her chair, and stretched.

"I don't think I can face starting the decryption right now," she said. "I need a caffeine injection as a matter of some urgency, and this time I'm buying."

"Good idea."

Mallory stood up as well, closed the lid on his laptop and unplugged the charger cable, then slid the computer back into his bag.

Robin looked at him quizzically.

"I can't afford to lose this machine," Mallory said simply. "I do a lot of my work for my clients offsite, and so I have a lot of commercially sensitive material on this computer as well as some expensive utility programs, plus all my personal stuff. So where I go, the laptop goes."

"Even fifty yards down the road for a coffee?"

"Even fifty yards down the road for a coffee," Mallory confirmed.

Robin locked the apartment door behind her and at the bottom of the spiral staircase she opened the rear door to the shop and led the way inside.

A pleasant-looking middle-aged woman turned around from her seat behind the counter as they walked in, lowering the novel she had been reading as she did so.

"Betty," Robin said, "this is David Mallory. He's helping me with a little project I'm working on." She turned to Mallory. "Betty runs the place," she went on. "I simply couldn't manage the shop without her. I know that's a cliche, but in this case it also happens to be absolutely true."

The coffee in the cafe Robin had selected was far better than it had been in the one where they had met. Somewhat revived and fortified, they were back in her office within twenty minutes, and Mallory started work on the decryption almost immediately. And almost immediately he ran into problems.

"You're quite right," he said. "It's only the first nine words that I can decode using the Atbash cipher with the eleven-place shift to the left. It doesn't work for the tenth word, nor the eleventh or twelfth." He thought for a few seconds, then continued. "I suppose realistically there are only two possibilities. Either whoever wrote this switched to a different type of encryption method, or they simply used a different shift but carried on using Atbash."

"If it's medieval, and I still think that's the most likely period, then I have no idea what other possible types of cipher were around, if any. Do you know?"

"Oddly enough, yes. Ciphers of various sorts have been around for a long time. Researchers have identified three kinds of monoalphabetic ciphers in the Old Testament, and there are even records of an early type of steganography-that's a technique for hiding a message inside another medium-using wax tablets from around the fifth century BC. The idea was to scratch the real message in plaintext on a block of wood used as the backing for a wax tablet, then apply the normal wax surface to hide it and write another, entirely innocent, message on the wax. Melt the wax off the wood, and then the important message could be read."

Mallory laughed shortly.

"That was a fairly efficient method of sending a hidden message, because it could travel as fast as the messenger could run or a horse could gallop, but there was another classic example of steganography that was a lot slower. According to Herodotus, in ancient Greece a vital message about Persian invasion plans was tattooed on the shaved scalp of a slave. Weeks later, when his hair had grown long enough to hide the tattoo, he was sent off to the recipient of the message, his head was shaved again, and the warning was delivered, but that was obviously a really slow option."

"I've actually heard of steganography," Robin said. "That includes things like microdots, doesn't it?"

"Microdots and almost everything else, yes. There was a famous case back in the sixties when an American serviceman who'd been captured by the North Vietnamese blinked his eyelids to spell out the word torture in Morse code during a press conference he was forced to attend, which is one of the more unusual examples. These days, because of digital transmission media, you can hide data or images in almost everything from pictures to sound files and documents.

"One very simple and obvious way of doing that would be to include a passage of text in a blank area of a word-processing document, and to make the text the same color as the background. It would be invisible to anyone reading the document, but if the recipient knows where it is he can simply highlight the block, change the text color, and read it. But more usually the text would be shrunk down to the size of a full stop or other punctuation mark and embedded somewhere in a document, or reduced to the size of a single pixel and then hidden in an image file of some type.

"Then there was a thing called a Polybius square, developed by a Greek historian in the second century BC, which was used to convert letters into numbers, most commonly employed in signaling. A variant of that is still in use today. And it was most probably Julius Caesar who used what you might call a shifted Atbash in his military communications, usually without reversing the cipher alphabet, and a monoalphabetic cipher of that kind is still known today as a Caesar alphabet. He also did things like substituting Greek for Latin letters. Coming a bit more up to date, the Vikings used simple encryption methods in some of their rune stones, and in the thirteenth century, Roger Bacon wrote quite a lot about the cryptography methods that were then in common use. Techniques for encrypting messages and information have been around in various forms for a long time. There's even a section in the Kama Sutra about the importance of using and understanding ciphers."

"The Kama Sutra?" Robin asked. "I thought that dealt with slightly more interesting subjects, like sex."

"It does." Mallory grinned. "And those are the only bits that everybody reads, but there's a lot more in that work than just finding the right-or even the wrong-position to adopt when you're in bed with somebody."

He looked back at the printed text in front of him.

"But almost all of these methods were various types of substitution ciphers," he finished, pointing at the paper he had been scribbling on, "and I'm pretty certain that this is just a kind of Atbash, nothing more complicated than that. And using this method of shifting, there are only twenty-six possible alternative keys, or fifty-two if we include the nonreversed cipher alphabets. I'll write out all of them and then we'll pick a word that's fairly short, four or five letters, something like that, and try each of them until we find the one that decodes it."

Writing them all out was laborious, but easy, not least because Robin did half of them.

"I'll start from the beginning," Mallory said, "with a right shift of one place, and see where that gets us."

The short answer was nowhere, because it didn't work. Nor did the right shift of two, but when he tried the next possible key, right-shifted three places, the first four-letter word he had selected deciphered as deus.

"That looks like Latin," he said.

"That's because it is," Robin confirmed. "It's the Latin word for God."

Mallory quickly decoded the nine words that followed the first group he had deciphered.

"If the guy who wrote this was following a pattern," he said, "I'll probably need to use a different key for the next word."

But to his surprise, he decrypted the next word, the nineteenth in the manuscript, using the same key, and did the same with the following eight. However, the twenty-eighth word refused to decipher using that key, and Mallory took several minutes, trying each possible Atbash key until it finally yielded to a left shift of seven. That worked for the next eight words, but not for the ninth.

"That's interesting," he said. "There's obviously something important about the number nine, because I've now used three different Atbash ciphers, two of them decoding nine words each and the other one decoding eighteen, which is of course nine multiplied by two. I'll bet this cipher works either for nine words or for a multiple of nine."