The letter sent by the sectaries was pathetically easy to unravel, and scarcely interesting; had I known what it contained I would never have bothered as it was not worth di Pietro’s life or the trouble his murder caused me. It spoke of preparations in that pompous language so beloved of sectaries, and referred elliptically to a place I confidently identified as Northampton. But there was little meat, nothing which justified the risk I had taken. If that lay anywhere, it was in the last, mysterious letter; I was determined to read it, and knew I must have the key.

Matthew came to me as I sat at my desk, the unreadable letter in front of me in all its defiance, and asked whether he had done well.

“Very well,” I told him. “Very well indeed, although largely by chance—your letter is uninteresting; it is this other one which fascinates me.” I held it up for him to examine, which he did with his habitual neatness and care.

“You know this already? You have unraveled it all?”

I laughed at his faith in me. “A different letter, a different source and, no doubt, a different addressee. But I know nothing and have unravelled less. I cannot read this letter. The code is based on a book, which determines the sequence of the cipher.”

“Which book?”

“That I do not know, and unless I can find out, I will understand nothing. But I am sure it is important. This sort of code is rare; I have come across it only a few times, and then written by men of the highest intelligence. It is too complex for fools.”

“You will succeed,” he said with a smile. “I am sure of that.”

“I love you for your confidence, my boy. But this time you are wrong. Without the key, the door will remain locked.”

“So how do we find this key?”

“Only the person who wrote it, and the person who will read it, will know what it is and have a copy.”

“So we must ask them.”

I thought he was joking and began to reprove him for his levity, but I saw in his face that he was quite serious.

“Let me return to Smithfield. I will tell them that there was an attempt to steal the letter which failed. And I will offer to go myself on the boat, to guard it and ensure it comes to no harm. Then I will discover to whom this one is sent, and what is the key.”

The mind of youth sees in such a simple and direct way that I could hardly conceal my amusement.

“Why do you laugh, doctor?” he asked, his brow furrowing. “What I say is right. There is no other way of discovering what you need to know, and you have no one else to send.”

“Matthew, your innocence is charming. You would go, you would be discovered and all would be lost, even if you escaped unharmed. Do not bother me with such foolishness.”

“You treat me always like a child,” he said, saddened by my remark. “But I can see no reason for it. How else can you discover what this book is, and who it is sent to? And if you cannot trust me, who else can you send?”

I took him by the shoulders and looked into his angry eyes. “Do not be upset,” I said, more gently. “I spoke as I did not out of contempt, but concern. You are young, and these are dangerous people. I do not wish you to come to harm.”

“I thank you for it. But I desire nothing more than to do something of value for you. I know my debt to you and how little I have repaid it. So please, sir, give your permission. And you must decide fast; the letters must be returned, and the boat leaves tomorrow morning.”

I paused, and studied his fair face, its perfection spoiled by his resentment, and knew from the sight more than from his words that I would have to loosen the bonds, or lose him forever. Still, I tried one more time.

“ ‘If I be bereaved of my children, I am bereaved’ “ (Genesis 43:14).

He looked at me gently, and with such kindness; I remember it still.

“ ‘Provoke not your children to anger, lest they be discouraged’ “ (Colossians 3:21).

I bowed to that, and let him go, embracing him as he left, and watching from my window as he walked down the street outside, until he was lost from sight in the crowds. I saw the spring in his step, and the joy in his walk that came from his freedom, and I grieved over my loss. I spent the afternoon in prayer for his safety.

I did not hear from him for a whole fortnight, and was tormented by distress and fear every day, lest the boat had sunk, or he had been discovered. But he acquitted himself better than I had expected and showed more skill than many an intelligencer properly waged by the government. When I received his first letter I wept with both relief and pride.

“Most reverend sir,” the letter began, Following your instructions, I shipped aboard the bark Colombo and made my way to the Hague. The crossing was terribly bad, and at one stage I was sure the mission would fail because it seemed certain the ship would sink with all hands. Fortunately the master was an experienced man and brought us through safely, if very ill.

By the time we docked, I had thoroughly ingratiated myself with this man and learned that he did not wish to spend much time in port. He was distressed about the death of di Pietro, concerned for his job and wanted to head back for London as swiftly as possible. So I offered to deliver the letters to their destination on his behalf, saying I would be glad of the chance to spend some time in this part of the world. As he had no notion there was anything special about any of them, he agreed readily and says he will bring me back to London when he comes over with his next load of good’s.

We went through the list as properly as any post officer, and checked the addresses of each envelope against the list he had in his hand.

“This one has no address,’’ I told him, picking up the letter which interests you so much.

“Nor it has. But no matter, it is here on my list.”

And he pointed out for me to see that he had instructions, in di Pietro’s own handwriting, that this particular letter was to be delivered to a man called Cola, in Guldenstraat.

Sir, I must tell you that the house concerned is that of the Ambassador of Spain, and that this Cola is well known there. I have not yet delivered it, for I was told he would not be there until tomorrow, so I refused to hand it over, saying I was under strict instructions to give it into his hands alone. In the meantime, I have prevailed on the English in this place to give me lodging, which they agreed to with great friendliness, for they feel cut off and anxious for any news of home.

When I return I will of course call upon you to offer such further news as I have found. Please be assured, dearest and kindest sir, etc. etc….

Even though the affection of my dear boy’s salutation warmed me, I fear I might have forgotten myself sufficiently as to box his ears with frustration had he been present. I realized that he had done a fine job; but nonetheless he had not succeeded as completely as I needed. I still did not have the name of the book that formed the key, and without that I was not greatly advanced. But, however much he had failed in this, I realized he more than made up for it elsewhere. For I knew that the Ambassador of Spain, Esteban de Gamarra, was an implacable, dangerous foe of England. That one piece of information alone justified everything I had done so far. For this Cola, I had been told months earlier, was associating with radicals, and now here he was with an address at the Spanish embassy. It was a fascinating puzzle.

The information placed me in a quandary, because if I had disobeyed by pursuing di Pietro, interfering in this matter was even more grave. Mr. Bennet was still my sole protector and I could not afford to lose his good will if I could not replace him with someone better. However, any form of link between the Spanish and the radicals was of the utmost seriousness. The prospect of an alliance between the upholder of Catholicism and the most fervent fanatics of Protestantism was hardly to be countenanced, but nonetheless I held in my hand the first faint glimmerings of such a connection, and I could not allow what seemed unlikely in abstract to overawe the most direct and compelling evidence.