7

"I beg your pardon," Sandra said, "I thought perhaps you had the rest of the mission laid out already."

"If only!" I sighed. "If I could solve murders involving espionage by following a recipe, Sandra, even the dozy sods at Scotland Yard could do it. As a rule, I plan my assignment one move at a time," I continued. "I have a purpose in mind and an overall impression of how to get there, but any new advance can make me change my ideas. For example, I was planning to stay in London for at least another few days, but the sudden and dramatic visit from Hector Nelson has changed my mind."

"How?" Sandra asked.

"His attendance, in camouflage, no less and that of his followers served as a warning that direct inspection in the city might involve grave danger while encouraging inadequate palpable compensation."

"I see."

"But the information Nelson gave us alternative lines of thought that already seemed promising to me, and these thoughts make our presence in London somewhat less essential at the moment than it otherwise may have been."

"I didn't realise you had formed any theory about the crime," Sandra said, surprised ", let alone one which Nelson could have supported."

"I had been thinking about this assignment since long before I met Brian Flynn," I replied. "Most of my initial ideas were queries such as: Why was an MI6 operative missing for seven days or more before somebody started looking for her? Why were the Metropolitan Police sent to an MI6 safe house in search of an MI6 agent? Why so much slur in the media about what police unearthed in the flat where they uncovered the body? Why has their probe made so little advancement? Why are absurd concepts about a sex game gone wrong still in distribution? And why have we even heard of this untruth at all?"

"An impressive list of questions," Sandra said.

"The mere tip of the iceberg," I told her. "There are many other crucial questions, but these are among the most vital." I paused and listened to the comforting sound of the train while I contemplated the scope and nature of the task ahead of us. "Fortunately," I continued, "this is an assignment in which the total appears to be less than the entirety of its portions."

"I don't follow you," Sandra told me with honesty.

"Perhaps it's not the best correlation," I restarted, "but I mean to say, if I tried to answer each problem independently, I would go mad trying. But that would be a fabricated tactic anyway because these questions are not reciprocally objective. Instead, they are all familiarly associated, and consequently, the only truly adequate clarification must answer them all concurrently."

"This sounds like a big problem, Quintus."

"Is it? If there happens to be enlightenment which answers all these questions, then surely it will not be challenging to find."

"Have you tried to verbalise any such answer?" she asked. "If so, I'd be happy to hear it."

"Occasionally, it helps to re-phrase the problems," I said, "and to step back and look at them from a diverse viewpoint. For example, I've been requesting why undeniable issues have occurred. Suppose we were keen about deferring deliberation about the reasoning for a time and distillate on the suspects and their competencies. We might find ourselves with numerous lines of contemplation, all consecutively moving in the same direction. Who could commit such a daring crime in an MI6 safe house for a start and get away unnoticed? Who could incapacitate all the observation methods? Who could make sure that nobody would check on Tina Davis when she stopped going to work? Who could establish false narratives about the crime scene throughout the media without fear of reprisal? Who could keep sex games gone wrong appearing in the headlines, even though it makes no sense? Who could have blocked this story but chose to let it play out in public? Who could interfere with a police investigation? Who could hide witnesses from Scotland Yard? Who could assign Hector Nelson to run a team that are not all qualified to investigate this case? Are there Russian secret agents handling Scotland Yard's case assignments? Is there a direct feed from the Chinese Minister of Propaganda to the British media? Could a militant Irish Republican faction stop MI6 from checking on an employee who hadn't turned up for work? Could bearded madmen in caves half a world away have done any of this?"

I paused again, and we listened to the clackety-clack of the wheels while I tried to grasp what I had just said.

"The implications are staggering," Sandra said nervously.

"Let them rest, Sandra", I replied. "What else have you been wondering about?"

"It may seem a small thing," Sandra said, "and it may be a minor thing. But as you asked, I'm curious about the arrangements you made for meeting Hector. Things happened so fast; I may have overlooked something, but it seemed to me you set up a secret way for him to beckon you, but no way for you to communicate with him."

"Sometimes you are more attentive than I give you credit for, Sandra," I said, "but yes, that's exactly right."

"I was speculating why you did it that way," she continued, "if you don't mind my asking."

"I don't mind at all," I said. "In this case, Sandra, Hector is a senior Scotland Yard detective who's come to me in disguise and was followed! His life is in more danger than mine."

"Do you think so?" Sandra asked.

"Yes." I answered, "The situation is dire, and Hector is disrupting the plans of some very influential people.".

"As you say, things are happening very fast," I continued. "That was because that's what I wanted them. The longer we kept those two men waiting, the likelihood they would have realised we were onto them, and the greater the chance they would have followed Hector. I may be wrong, and perhaps if I'd left them standing for too long, they might have fallen asleep! But I wasn't willing to take those sorts of risks. However, I wanted to keep things simple for Hector. So I set up a code that only he can use once so he can contact me," I carried on, "and I hope he'll come to our next meeting alone, which would give me more time. Then, when I meet him again, I will give him another code."

"How does this code of yours work?"

"It is simple, and yet it's not," I replied. "The main disadvantage with one-time codes is the fact I can only use them once. After that, you need a new key for each message."

"And the key is?"

"The key is the intelligence that answers the message," I explained. "Sometimes, the key might be the password. But there are other keys as well; it might be a phrase, or a sequence of numbers, or even something more uncommon."

"And you need a new one each time?" she asked. "That must be troublesome."

"It is," I said, "and even more problematic, the key must be at least as long as the communication itself. But on the other hand, an appropriately assembled one-time code is unbreakable encryption. Do it correctly, and it's unequivocally impossible to break, the only means of encoding that can make this claim. For some functions, the protection is well worth the money. The present state," I continued, "calls for the maximum insurance possible. Encryption so dependable that our communication can essentially be transmitted!"

"Transmitted?" I asked.

"Hector will put an ad in the paper. Thousands of people will see it, but they won't understand it. So only Hector and I will."

"How can you be so sure?"

"Because it's a one-time code," I reminded her. "If you don't have the key, you cannot understand it!"

"Forgive me," Sandra said, "but I still don't comprehend. Can you give me an instance?"

I wrote on a piece of paper and handed it to Sandra. "It could be as simple as this," I said.

She looked at the paper and read it aloud:

Summer,

I will be away until Tuesday.

Sapphire

"What is this, a joke?" she asked. "These are my sister's children's names."

"I know," I replied. "But, as long as both Hector and I have the same key, and nobody else does, we could use any message at all. It's the key that matters. In a one-time code, the key is virtually everything."

"And with this?"

"Summer would mean Quintus; Sapphire would mean Hector. I will be away until would mean, please meet me at the Griffin in Whetstone pub at eight o'clock on; and now you can see, can't you, Sandra, that the only true word contained in the message is the word Tuesday."

"It is very clever," Sandra admitted.

"It is ancient," I replied. "But still works!"