"Perfectly good specimens and extremely valuable," he interrupted, "but don't get side-tracked. I know what they are for: you don't. Tell me what happened."

I took a sip of my rapidly cooling tea, and put down the mug.

"I found the row of bottles," I continued, "all in the locked cupboard. Neatly labelled, A, B, C. I poured exactly three measures from A into the medicine-glass, and that was that. I swallowed it, replaced the bottle and glass, locked the cupboard, locked the lab, and waited for something to happen. Well, nothing did." I paused, to let this information sink in. No comment from Magnus.

"So," I went on, "I went into the garden. Still no reaction. You told me the time factor varied, that it could be three minutes, five, ten, before anything happened. I expected to feel drowsy, although you hadn't specifically mentioned drowsiness, but as nothing seemed to be happening I thought I would go for a stroll. So I climbed over the wall by the summer-house into the field, and began to walk in the direction of the cliffs."

"You damn fool," he said. "I told you to stay in the house, at any rate for the first experiment."

"I know you did. But, frankly, I wasn't expecting it to work. I planned to sit down, if it did, and drift off into some delightful—"

"Damn fool," he said again. "It doesn't happen that way."

"I know it doesn't, now," I said.

Then I described my whole experience, from the moment the drug took effect to the smashing of the glass in the basement kitchen. He did not interrupt me at all except to murmur, when I paused for breath and a sip of tea, "Go on.. go on.."

When I had finished, including the aftermath in the boiler-room, there was complete silence, and I thought we had been cut off. "Magnus," I said, "are you there?"

His voice came back to me, clear and strong, repeating the same words that he had used at the start of our telephone session.

"How splendid," he said. "How absolutely splendid. Perhaps…" The truth was that I was completely drained, exhausted, having been through the whole process twice.

He began to talk rapidly, and I could just imagine him sitting at that desk of his in London, one hand holding the receiver, the other reaching out for his inevitable doodling-pad and pencil.

"You realise", he said, "that this is the most important thing that has happened since the chemical boys got hold of teonanacatl and ololiuqui? These only push the brain around in different directions — quite chaotic. This is controlled, specific. I knew I was on to something potentially tremendous, but I couldn't be sure, having only tried it on myself, that it wasn't hallucinogenic. If this was so, you and I would have had similar physical reactions — loss of touch, greater intensity of vision, and so on — but not the same experience of altered time. This is the important thing. The tremendously exciting thing."

"You mean", I said, "that when you tried it on yourself you also went back in time? You saw what I did?"

"Precisely. I didn't expect it any more than you did. No, that's not true, because an experiment I was working on then made it remotely possible. It has to do with D.N.A., enzyme catalysts, molecular equilibria and the like — above your head, dear boy, I won't elaborate — but the point that interests me at the moment is that you and I apparently went into an identical period of time. Thirteenth or fourteenth century, wouldn't you say, judging from their clothes? I too saw the chap you describe as your horseman — Roger, didn't the Prior call him? — the rather slatternly girl by the fire, and someone else as well, a monk, which immediately suggested a tie-up with the mediaeval priory that was once part of Tywardreath. The point is this: does the drug reverse some chemical change in the memory systems of the brain, throwing it back to a particular thermodynamic situation which existed in the past, so that the sensations elsewhere in the brain are repeated? If it does, why does the molecular brew return to that particular moment in time? Why not yesterday, five years ago, or a hundred and twenty years? It could be — and this is the thing that excites me — it could be that there is some very potent link connecting the taker of the drug with the first human image recorded in the brain, while under the drug's influence. In both our cases we saw the horseman. The compulsion to follow him was particularly urgent. You felt it, so did I. What I don't yet know is why he plays Virgil to our Dante in this particular Inferno, but he does, there's no escaping him. I've made the 'trip'—to use the students' phraseology — a number of times, and he's invariably there. You'll find the same thing happens on your next adventure. He always takes charge." The assumption that I was to continue acting as guineapig for Magnus did not surprise me. It was typical of our many years of friendship, both at Cambridge and afterwards. He called the tune, and I danced, in God only knew how many disreputable escapades in our undergraduate life together, and later when we went our separate ways, he to his career as a biophysicist and thence to a professorship at London University, I to the tamer routine of a publisher's office. My marriage to Vita three years ago had made the first break between us, possibly a salutary one for us both. The sudden offer of his house for the summer holidays, which I had accepted gratefully, being between jobs — Vita was urging me to accept a directorship in a flourishing New York publishing firm run by her brother, and I needed time to decide — now appeared to have strings attached. The long, lazy days with which he had baited me, lying about in the garden, sailing across the bay, were beginning to take on another aspect.

"Now look here, Magnus," I said, "I did this for you today because I was curious, and also because I was on my own, and whether the drug had any effect or not didn't matter one way or the other. It's quite out of the question to go on. When Vita and her children arrive I shall be tied up with them."

"When do they come?"

"The boys break up in about a week. Vita's flying back from New York to fetch them from school and bring them down here."

"That's all right. You can achieve a lot in a week. Look, I must go. I'll ring you at the same time tomorrow. Goodbye."

He had gone. I was left holding the receiver, with a hundred questions to ask and nothing resolved. How damnably typical of Magnus. He had not even told me if I must expect some side-effect from his hell-brew of synthetic fungus and monkeys' brain-cells, or whatever the solution was that he had extracted from his range of loathsome bottles. The vertigo might seize me again, and the nausea too. I might suddenly go blind, or mad, or both. To hell with Magnus and his freak experiment… I decided to go upstairs and take a bath. It would be a relief to strip off my sweaty shirt, torn trousers, the lot, and relax in a tub of steaming water primed with bath-oil— Magnus was nothing if not fastidious in his tastes. Vita would approve of the bedroom suite he had put at our disposal, his own, in point of fact, bedroom, bathroom, dressing-room, the bedroom with a stunning view across the bay.

I lay back in the bath, letting the water run until it reached my chin, and thought of our last evening in London, when his dubious experiment had been proposed. Previously he had merely suggested that, if I wanted somewhere to go during the boys' school holidays, Kilmarth was mine for the taking. I had telephoned Vita in New York, pressing the offer. Vita, not altogether enthusiastic, being a hot-house plant like many American women, and usually preferring to take a vacation under a Mediterranean sky with a casino handy, demurred that it always rained in Cornwall, didn't it, and would the house be warm enough, and what should we do about food? I reassured her on all these points, even to the daily woman who came up every morning from the village, and finally she agreed, chiefly, I think, because I had explained there was a dish-washer and an outsize fridge in the lately converted kitchen. Magnus was much amused when I told him.

Three years of marriage, he said, and the dish-washer means more to your conjugal life than the double bed I'm throwing in for good measure. I warned you it wouldn't last. The marriage, I mean, not the bed. I skated over the somewhat thorny topic of my marriage, which was going through a period of reaction after the first impulsive, passionate twelve months, for if it was thorny this was largely because I wanted to remain in England and Vita wanted me to settle in the States. In any event, neither my marriage nor my future job concerned Magnus, and he passed on to talk about the house, the various changes he had made since his parents had died — I had stayed there several times when we were at Cambridge — and how he had converted the old laundry in the basement to a laboratory, just for the fun of it, so that he could amuse himself with experiments that would have no connection with his work in London. On this last occasion he had prepared the ground well with an excellent dinner, and I was under the usual spell of his personality, when he suddenly said, "I've had what I think is a success with one particular piece of research. A combination of plant and chemical into a drug which has an extraordinary effect upon the brain."

His manner was casual, but Magnus was always casual when he was making some statement that was important to him.

"I thought all the so-called hard drugs had that effect," I said. "The people who take them, mescalin, L.S.D., or whatever, pass into a world of fantasy filled with exotic blooms and imagine they're in Paradise."

He poured more brandy into my glass. "There was no fantasy about the world I entered," he said. "It was very real indeed." This piqued my curiosity. A world other than his own egotistical centre would have to possess some special attraction to draw him into it.

"What sort of world?" I asked.

"The past," he answered.

I remember laughing as I cupped the brandy glass in my hand. "All your sins, do you mean? The evil deeds of a misspent youth?"

"No, no," he shook his head impatiently, "nothing personal at all. I was merely an observer. No, the fact was.." he broke off and shrugged his shoulders. "I won't tell you what I saw: it would spoil the experiment for you."

"Spoil the experiment for me?"

"Yes. I want you to try the drug yourself and see if it produces the same effect."

I shook my head. "Oh, no," I told him, "we're not at Cambridge any more. Twenty years ago I might have swallowed one of your concoctions and risked death. Not any more."

"I'm not asking you to risk death," he said impatiently. "I'm asking you to give up twenty minutes, possibly an hour, of an idle afternoon, before Vita and the children arrive, by trying an experiment on yourself that may change the whole conception of time as we know it at present." There was no doubt that he meant every word he said. He was no longer the flippant Magnus of Cambridge days: he was a professor of biophysics, already famous in his particular field, and, although I understood little if anything of his life's work, I realised that if he really had hit upon some remarkable drug he might be mistaken in its importance, but he was not lying about his own evaluation of it.

"Why me?" I asked. "Why not try it on your disciples in London University under proper conditions?"

"Because it would be premature," he said, "and because I'm not prepared to risk telling anyone, not even my disciples, as you choose to call them. You are the only one to know that I'm even thinking along these particular lines, which is way outside the stuff I usually do. I stumbled on this thing by chance, and I've got to find out more about it before I'm even remotely satisfied that it has possibilities. I intend to work on it when I come down to Kilmarth in September. Meanwhile, you're going to be alone in the house. You could at least try it once, and report back. I may be entirely wrong about it. It may have no effect upon you except to turn your hands and feet temporarily numb and make your brain, such as you possess, dear boy, rather more alert than it is at present."

Of course in the end, after another glass of brandy, he had talked me into it. He gave me detailed instructions about the lab, he gave me the keys to the lab itself and to the cupboard where he kept the drug, and described the sudden effect it might have — no intervening stage, but direct transition from one state to another — and he said something about the after-effects, the possibility of nausea. It was only when I asked him directly what I was likely to see that he became evasive. "No," he said, "it might predispose you, unconsciously, to see what I saw. You've got to make this experiment with an open mind, unprejudiced."