Sir Francis, however, had not forgotten me. The next day, as we prepared to return to the hospital after our midday meal, Phelippes’s serving man, whom I now knew as Thomas Cassie, arrived with a summons for me.

‘Master Phelippes needs me this afternoon?’ I said. I was anxious to return to my patients and resented being fetched away like this.

‘No, Master Alvarez. It is Sir Francis himself who wishes to see you.’

My heart quickened uncomfortably in my chest. Why should Sir Francis want to see me? After that first interview, my dealings had been entirely with Thomas Phelippes, although Sir Francis would look into the office from time to time and discuss our work with us. Had Poley said something to betray me? I looked at my father for guidance.

‘Of course you must go, Kit,’ he said. ‘Don’t worry. I do not have too much work this afternoon. I can check your patients for you.’

No escape, then. Nevertheless, I picked up my satchel of medical supplies, in case there would be time for me to go to the hospital after seeing Sir Francis, and I followed Cassie out into the street. The increasing warmth of the sun brought the stench of the Smithfield slaughterhouses coiling about us. Leaving home now in answer to this unexpected summons, I was suddenly reminded of that other summons, back in January, when Simon had fetched me to the Marshalsea, setting all of this in motion. I had not seen Simon for some time, not since before the measles epidemic, and I found myself wishing quite painfully that we could meet again. Could we be friends? I knew so few people of my own age, apart from Peter Lambert at the hospital and Sara Lopez’s daughter Anne. Somehow I had warmed to Simon, strange as it seemed, when we came from such different worlds. Perhaps I would seek him out one day soon. But I did not question my reasons too closely.

Cassie left me at the door of the room which Sir Francis used as an office. I knocked and was told to come in. The room seemed unchanged since my nervous interview there weeks before, except that the gloomy winter light had been replaced by a cheerful sun which created a bright haze behind Sir Francis’s dark head. As I became accustomed to the dazzle, I noticed a few silver glints amongst the thick dark brown thatch of his hair and beard. He looked even more worn than when I had last seen him, his eyelids red as if he had been rubbing them and his skin pallid. He could not have been outside in this fresh new spring air, except on his hurried journeys to and fro to consult with the Queen or Lord Burghley.

‘Come in, Kit, come in.’ He got up and came round to the front of his desk, drawing two chairs together and sitting in one of them. He motioned me to the other.

When I was seated, wondering what on earth he could want with me, he said, ‘Thomas Phelippes is very pleased with your work. You are quick and neat, and have an excellent skill in deciphering new codes.’

I blushed and murmured something. Phelippes had never told me this himself.

‘You will have guessed,’ he went on, ‘that our work here has many strands, not just the interception of treasonous letters and the breaking of codes. I have informants in all the main countries of Europe, especially those which threaten us: France, Spain, the Spanish Netherlands, and the Papal States.’

I nodded, wondering where this was leading.

‘Here at home we also place informants where they can discover any plots that may be brewing amongst traitors on our own shores. I believe when you first encountered Robert Poley, he was imprisoned in the Marshalsea.’

‘Yes.’ My voice came out strained, for I did not care to remember that encounter. ‘I was summoned to attend him. At least, my father was, but he was attending Lord Burghley and I went in his stead. Poley believed he had been poisoned.’

‘The keeper sent for your father?’

‘He sent a boy with a message.’ Instinctively I decided to keep Simon’s name out of it.

‘And had he been poisoned?’

‘Oh, no. He had eaten bad oysters. I purged him.’

‘He cannot have enjoyed that.’ Sir Francis gave a small smile. ‘At any rate, he recovered quickly. I believe Thomas has told you that Poley had been placed in the Marshalsea to find out what he could from the Catholic priests held there, posing as a Catholic sympathiser himself. These priests are smuggled into the country by an organisation in France run by one William Allen, who hates our Queen, our church, and the country of his birth. Although these priests claim to be here merely to minister to the English Catholics, many are trained soldiers and assassins who would overthrow the state.’

I nodded again. The activities of these men were widely talked about, although popular opinion probably differed widely from the knowledge Sir Francis held buttoned up in that dark doublet of his.

‘Now Poley has been introduced into the household of my son-in-law. The Catholic faction in France believes he is working for them amongst Sidney’s circle, but he is one of my informants.’

It seemed unnecessary to say that Phelippes had already told me something of Poley’s activities. I was still unsure why we were having this conversation, but I risked speaking out. ‘Is Poley quite to be trusted, sir? I have never felt he is altogether honest.’

I held my breath. Sir Francis might be very angry at what seemed to be my questioning of his judgement. Instead, he looked at me keenly.

‘You are not the only one to think so. I handle him – and his information – with care.’

There was silence for a moment as Sir Francis pressed his palms together and tapped his fingers against his lips.

‘I believe you suffered at the hands of the Inquisition in Portugal, did you not?’

I shuddered uncontrollably and looked away. ‘That is so,’ I whispered.

‘So you can have no love of the Catholic church and its persecutions.’

‘No, sir.’

‘Would you be willing to undertake a similar mission as Poley and other informants? It would mean living for a time in a Catholic household and finding out what you could – whether there is any treason at work there.’

In astonishment, I stared at him. ‘But . . . I know nothing of how an informant works. I don’t think I could do it.’

‘Kit, how would you feel if one of the great Catholic powers should overrun this country, establish a Catholic monarch on the throne, and introduce the Inquisition here? For make no mistake about it, you and I would both receive their . . . attentions. Could you endure that a second time?’

I could feel the blood drain from my face. My heart began to pound and my hands shook. My tongue cleaved to the roof of my mouth and I could not speak.

He did not seem to expect an answer. Instead he rose from his chair and turned away from me to look out of the window.

‘I want to tell you a story. It’s a story you will have heard before, but I was there. I witnessed the horrors myself, and I have never, never forgotten them.’

He paused and looked back at me.

‘How old are you, Kit?’

‘Sixteen, sir.’ I managed to whisper the words.

‘Well, you would have been but two years old at the time, August 1572. You would have been living peacefully in a Portugal that was still an independent nation, before Spain seized control of the country. I was the Queen’s ambassador to the court of the French king Charles IX. He was king, but much of the power lay in the hands of his mother, Catherine de’Medici.’

He paused again and seemed to be looked at something beyond the window. Perhaps he was seeing Paris all those years ago. August 1572. I thought I knew what was coming.

‘We had a house in the Faubourg-Saint-Germain. That’s on the left bank of the Seine, not far from the great cathedral, Notre Dame de Paris. You won’t have been to Paris, of course. I was quite a young married man then and I had my family with me. My daughter Frances was five years old – she’s just three years older than you. My wife was expecting our next child and was feeling the heat of a Paris August, wishing she was at home in England. We had young Philip with us too, Philip Sidney. He would have been about eighteen then. Frances has known him all her life.’