by James Becker
Mallory picked up a fork and cut the end off the slice of Victoria sponge that Betty had just placed in front of him.
“One definition of insanity,” he said, swallowing the cake, “is doing the same thing over and over again and expecting a different result each time. I know that’s not exactly what we’re doing here, because we are trying different words, but I do get the feeling that we’re wasting our time. The problem is, Betty, that if the correct code words that we need to use are, for example, Temple Mount and Jacques de Molay, we not only need to know that, but also which one comes first, are they written forward or backward, do they come at each end of the alphabet, or are they used by themselves? There are just so many permutations that we could end up doing this not just for hours but for days or weeks. And there’s no guarantee that we’d crack it in the end.”
“So have you got any other ideas?” Robin asked.
Mallory took a sip of coffee before he answered.
“That is good coffee,” he said. “Well, I have been kicking a few possibilities around. I think we can fairly definitely eliminate the more complex types of encryption, things like double substitution or double transposition ciphers, where you use one code word or words to encrypt the original message, and then use a second code word or words to encrypt the encrypted text, if you see what I mean. That’s basically quite a simple technique, but if you don’t know both the code words that have been used, it’s also virtually impossible to crack. Unless of course you got access to something like a Cray supercomputer that can mount a brute-force attack and perform tens of millions of calculations every second. My laptop is quite powerful, but it’s several orders of magnitude too slow to try anything like that.
“In fact,” he went on, “you can even add an extra layer of complication to this technique. Some messages encrypted using double transposition contain a very short piece of plaintext right at the beginning, sometimes just six numbers or occasionally six numbers split into two groups of three and preceded by the letters P, L, and W. Those refer to the page, line, and word, which is a way of telling the recipient of the message exactly what words are being used as code words for the two stages of encryption. The only thing that requires is that both the sender and the recipient must have copies of precisely the same book, and precisely the same edition, so that the particular word referred to will be the same in both volumes. But with the millions of books that have been published over the centuries, it wouldn’t be at all surprising if two people possessed copies of precisely the same book. And, of course, from a counterespionage point of view, there is nothing even faintly incriminating about just another book, so that particular technique has been in use for quite some time. But I really don’t think that what we’re looking at here is anything like as complicated as that.”
“So what can you do?” Betty asked. “In fact, is there anything that you can do to solve it?”
“In the absence of any better ideas,” Mallory said, “I think the only thing we can do is just rely on frequency analysis. That will take some time, but unless I’m missing something, eventually it should start to produce results.”
“I have no idea what you’re talking about,” Betty said. “It is something to do with radios?”
Mallory gave her a smile, and shook his head.
“No, nothing like that,” he said. “You can produce a frequency analysis table for any language, and what that will do is list the most commonly used letters in the alphabet for that language. For example, in English the six commonest letters found in most pieces of text are E, T, A, O, I, N, which is what you’d expect because four of the five vowels are in that list. Of course, the frequency does depend upon the type of text being analyzed, because obviously a romantic novel, say, might throw up a slightly different set of letters to a property conveyance or a vicar’s sermon, but as a general rule that list works. So, maybe what we should be doing now is applying that same technique to the text we have in front of us.”
“I’m on it,” Robin said, opening up her laptop, selecting a search engine, and rapidly typing a phrase into the field at the top of the screen. Within about a second the results were displayed, and she tracked down the list of sites before choosing one that hopefully would give her what she wanted.
“This might do the trick,” she said. “It’s a website containing the results of an analysis that was performed on a collection of mixed-genre Latin texts, texts that amounted to well over a quarter of a million words. Interestingly, the result is not that dissimilar to English, with the six commonest letters in the Latin alphabet being I, E, A, U, T, S, so again four of the five vowels are in the list. In fact, those six letters weren’t just the commonest that the researchers identified in the text, but actually amounted to well over half of the letters used, and the first three letters—I, E, and A—accounted for almost one-third of the total. Luckily,” she added, “this particular analysis also lists all of the letters in the Latin alphabet and their frequencies.”
Betty looked at her slightly doubtfully.
“I think you told me a long time ago that the Latin alphabet changed over time, so how do you know that this list of letters will work for the text that we’re looking at?”
“You’re quite right,” Robin agreed, “and that may prove to be a problem. We’ll just have to wait and see. I suppose the good news is that the present twenty-six letters of the Latin alphabet became established during the Middle Ages, which is more or less the period that this piece of vellum has to date from. Before that time, in classical Latin there were only twenty-three letters, all but two of which were derived from a much earlier, Etruscan alphabet. The missing letters were J, U, and W, which of course isn’t a double U at all, but a double V. Today those twenty-six letters form the English alphabet and are also the most important part of the character set of most other European languages.”
“So if you want to be pedantic about it,” Mallory chimed in, “that Roman chap who turned up and proclaimed, Veni vidi vici—‘I came, I saw, I conquered’—wasn’t actually called Julius Caesar at all, but Iulius Caesar, because when he was around the letter J hadn’t been invented.”
“That sounds like a typical nitpicking objection,” Robin said. “The kind of thing you get on a pub quiz night when the bloke who came second is arguing the toss over the answer to one question.”
“Just trying to get things right. Anyway, let’s see if we get anywhere with frequency analysis.”
Robin took a fresh piece of paper and wrote out the complete frequency table that she had found on the website.
“If you think this is going to work,” Betty said, “why didn’t you try this right from the start?”
Mallory shook his head.
“We could have done,” he agreed, “but it’s a bit of a hit-and-miss process, not to mention pretty dull and boring, and Robin and I both thought that if we could guess the words the medieval scribe had used to encrypt the text, we’d get a result a lot faster. What we have to do now is go through the entire encrypted piece of Latin, letter by letter, and count the frequency of each one. Then we have to apply the frequency analysis table and write out the whole thing again, this time with the letters that we think are the plaintext versions of the encrypted Latin, and just see if it makes any better sense.”
“And we might have to do that more than once,” Robin said, “because although we might well end up identifying the vowels fairly accurately, it’s the consonants that give the language its shape, and frequency analysis gets less and less accurate the further down the alphabet you get. So we’ll probably have to try a number of different letters in particular spaces in the text before we can identify exactly what each word is. And the other problem we have,” she added, pointing at the folded piece of vellum, “is that the author of that text used what’s known as scriptio continua, or continuous script. That means there are no gaps between words, because to include gaps would obviou
sly make decryption a lot easier, and the whole point of this message is that it should not be easy to decipher.”
Before starting, Robin placed each of the three sheets of paper containing Betty’s transcription of the text on the laser printer, and made half a dozen copies of each sheet using the photocopier function. Then she took a clean sheet of paper, checked that the pencil she’d picked up had a decent point, and waited for Mallory to start.
He took the first of the photocopied sheets and read out the first letter on the top line, which was the letter M. Robin noted that on her sheet, and then began recording every time that letter appeared in the ciphertext as Mallory read it out, using the simple and classic notation of four vertical lines and crossing them with a diagonal bar to make five as he identified each occurrence of the letter. While she did that, he drew a diagonal line through each letter M on the transcription as well, so ensuring that he didn’t miss any.
When he’d finished the first sheet, he repeated the same process, with the same letter, on the second sheet and then again on the third. And once he’d done that, he went back to the first sheet of the transcribed text again, read out the second letter, and began the process all over again.
It was, by any standard, an almost terminally boring occupation, and by five thirty that afternoon, with perhaps one-third of the transcription analyzed, Robin and Mallory both decided, at virtually the same moment, that enough was enough. At least for one day.
Betty shut down the catering facilities at the back of the shop, pulled on her coat, picked up her handbag, and left the premises, heading for the ferry that would take her to her small and comfortable terraced cottage on the opposite side of the river Dart.
Mallory and Robin left the building a couple minutes later, Mallory carrying the wooden chest, inside of which were both the piece of ancient vellum and all their notes. They walked around the back of the bookshop and up the spiral staircase to Robin’s apartment, where she placed the vellum in her safe while Mallory tucked away the medieval chest in an alcove. They knew they were going to spend a bit more time looking at the transcription and their notes when they returned to the apartment, so Mallory slid the papers into his computer bag, which he had decided to leave in the study while they ate their meal. It was peculiar, but since meeting Robin he had become noticeably less paranoid about always having his laptop computer with him. Though he still had some way to go: his most up-to-date backup hard drive was tucked away securely in the inside pocket of his jacket.
A few minutes after that, they retraced their steps and headed down toward the river frontage and one of the restaurants where they could enjoy an early dinner.
5
Dartmouth, Devon
Gary Marsh watched as the middle-aged and slightly plump woman left the bookshop, and he tracked her with his binoculars as she headed toward the ferry terminal. When Jessop and Mallory appeared, he abandoned the binoculars in the car and headed down the street toward them—Jessop, after all, was his primary target.
He watched them walk around the side of the building, Mallory carrying an old wooden chest, and guessed that they were making their way toward the apartment he knew was located directly above the shop. He didn’t make any attempt to follow them, just loitered on the main road waiting either for them to reappear or, if they intended to remain in the apartment for some time, for them to stay out of sight. Seven or eight minutes later, they stepped back onto the pavement from the side alley and headed for the center of the town, apparently oblivious to his presence.
He followed them on the opposite side of the road until they entered one of the many restaurants located near the water’s edge in Dartmouth. Once he was certain that they would be in the building for long enough to eat a meal—he’d seen them seated near one of the bay windows, the waiter handing each of them a large menu once they had sat down—he retreated about a hundred yards to a convenient low wall that was just the right height to sit on, and a vantage point that allowed him to still see the front entrance of the restaurant. Then he took out his phone to call his principal.
“Nothing much is happening now,” he began, “and that’s been pretty much the pattern for the entire day. They were in the bookshop for most of the afternoon, and right now they’re sitting down to a meal in a local restaurant that will be a hell of a lot better than the crisps and sandwiches that I’m just about to eat.”
“Okay. We’re interested in any deliveries Jessop might have received, especially any that might have come from abroad.”
Marsh thought for a moment or two before he replied. For some reason, he didn’t like the way the conversation was heading. He had a strong suspicion that if he told his principal about the two largish boxes that had arrived at the shop late that morning, the next step in the operation might well be a request for him to break in and find out what, exactly, had been delivered. But he also knew that he really had very little option.
“You do know that she sells books for a living, don’t you?” he asked. “She’s had about five packages arrive at the shop today, some of which I presume were books. In fact,” he added, embellishing the story somewhat, “I’m pretty sure that the last couple came from Amazon. Is that the kind of delivery you’re interested in?”
“Of course not. The shipments we’re watching out for will probably be quite large boxes, probably delivered by courier, and most likely with a Swiss address for the sender.”
“I pride myself on being largely invisible in most circumstances,” Marsh said, “but I promise you that if you want me to get close enough to the shop to read the information displayed on a delivery note, somebody is going to notice me. Binoculars and a parked car won’t do it. The best I can do for you is give a rough estimate of the size of anything that arrives at the shop. Don’t you have any other information, like the expected delivery time or what the package is supposed to look like?”
This time, the principal paused. Perhaps, Marsh wondered, he was taking instructions from whoever was pulling his strings, because he was quite certain that although the anonymous senior police officer was the man issuing orders and paying the bill, his every action was being directed by somebody else, somebody who remained even deeper in the shadows.
“We have no definite information about any of that. There is a possibility that Jessop may be sent a number of ancient documents that would probably fit inside a heavy-duty cardboard box with a capacity of perhaps two or three cubic feet or thereabouts. It is also possible that she might be sent a small wooden box or chest which would probably also be the same sort of size as the cardboard box. It would probably be packed inside protective covering, but if by any chance the box were visible, it would be clearly ancient and almost certainly bound with metallic reinforcing bands or decoration.”
“There were two deliveries late this morning that were similar in size to that,” Marsh said, thinking back to what he had observed. He had seen the delivery of two large packages that almost precisely matched the description that had just been supplied by his principal, and he had later seen Mallory leaving the bookshop carrying an ancient wooden chest with prominent metal reinforcing.
“You should have told me immediately that they were delivered.”
“I’m not a mind reader,” Marsh snapped. “I wasn’t aware that you were looking out for packages as well. My briefing from you told me I was to make the woman Robin Jessop my primary target for surveillance, with David Mallory as the secondary. And that’s what I did. You’re lucky I even bothered noting what was in her mail delivery.”
“Are they still in the restaurant?” the principal asked.
Marsh brought the pair of compact binoculars up to his eyes, focused the instrument on the front wall of the restaurant, and quickly located Robin Jessop. Mallory was partially out of sight behind a curtain, but Marsh had no doubt that the man was still there.
“Yes. It looks like their starters have just arrived.�
�
“Good. What we’d like you to do is to go to Jessop’s shop and apartment, right now, while they are out of the picture, get inside, and find that chest and the contents of that large cardboard box that was delivered this morning. And a word of warning. If you do find the chest, you may well also find that there’s some kind of an antitheft device, spring-loaded hidden sword blades or something of that sort, most likely concealed in the lid. So don’t just open it up and hope for the best.”
“That’s helpful, I suppose. So, how do I get the lid open to check what’s inside?”
“The information I have,” the principal said, “is that the booby trap, if there is one, is designed to target somebody opening the chest from the front, which is what you would usually do. So our advice is to use some kind of a tool to lift the lid, and stand behind the chest while you’re doing so.”
“You’re full of good news tonight,” Marsh said, “and just so you know, breaking and entering is not what you might call a specialty of mine. I can get a Yale lock open without too much trouble, but if she’s got deadlocks and stuff on her doors, the only way I’ll be able to get in is if I force them open or break a window or something. And that really falls outside my remit. If you want that done, you’re going to have to find somebody else. I value my freedom and my independence too much to commit an openly criminal act, no matter what fee you offer me.”
“Well, at least get over there and take a look. That’s not illegal, as far as I know.”
“You should know,” Marsh pointed out, “because you’re a copper. And something else you should know,” he added, “is that I’m calling you on my mobile and one of the apps I have running on the phone is a recorder, so everything you’ve said to me and everything I’ve said to you is now recorded on the data card. And another thing is that whenever I finish one of my telephone calls, the phone automatically uploads the audio file to the cloud, so there’s a permanent record of what we’ve said. Just thought you might like to bear that in mind.”