I went upstairs to the library and dialled the number of Magnus's flat. He answered immediately.

"How was it?" he asked.

"What do you mean, how was it? How was what? It rained all day."

"Fine in London," he replied. "But forget the weather. How was the second trip?"

His certainty that I had made the experiment again irritated me. "What makes you think I took a second trip?"

"One always does."

"Well, you're right, as it happens. I didn't intend to, but I wanted to prove something."

"What did you want to prove?"

"That the experiment was nothing to do with any telepathic communication between us."

"I could have told you that," he said.

"Perhaps. But we had both experimented first in Blue-beard's chamber, which might have had an unconscious influence So… So, I poured the drops into your drinking-flask — forgive me for making myself at home — drove to the church, and swallowed them in the porch. His snort of delight annoyed me even more.

"What's the matter?" I asked. "Don't tell me you did the same."

"Precisely. But not in the porch, dear boy, in the churchyard after dark. The point is, what did you see?"

I told him, winding up with my encounter with the vicar, the visit to the public library, and the absence, or so I had thought, of any side-effects. He listened to my saga without interruption, as he had done the day before, and when I had concluded he told me to hang on, he was going to pour himself a drink, but he reminded me not to do likewise. The thought of his gin and tonic added fuel to my small flame of irritation.

"I think you came out of it all very well," he said, "and you seem to have met the flower of the county, which is more than I have ever done, in that time or this."

"You mean you did not have the same experience?"

"Quite the contrary. No chapter-house or village green for me. I found myself in the monks dormitory, a very different kettle of fish."

"What went on?" I asked.

"Exactly what you might suppose when a bunch of mediaeval Frenchmen got together. Use your imagination."

Now it was my turn to snort. The thought of fastidious Magnus playing peeping Tom amongst that fusty crowd brought my good humour back again.

"You know what I think?" I said. "I think we found what we deserved. I got His Grace the Bishop and the County, awaking in me all the forgotten snob appeal of Stonyhurst, and you got the sexy deviations you have denied yourself for thirty years."

"How do you know I've denied them?"

"I don't. I give you credit for good behaviour."

"Thanks for the compliment. The point is, none of this can be put down to telepathic communication between us. Agreed?"

"Agreed."

"Therefore we saw what we saw through another channel — the horseman, Roger. He was in the chapter-house and on the green with you, and in the dormitory with me. His is the brain that channels the information to us."

"Yes, but why?"

"Why? You don't think we are going to discover that in a couple of trips? You have work to do."

"That's all very well, but it's a bit of a bore having to shadow this chap, or have him shadow me, every time I may decide to make the experiment. I don't find him very sympathetic. Nor do I take to the lady of the manor."

"The lady of the manor?" He paused a moment, I supposed for reflection. "She's possibly the one I saw on my third trip. Auburn-haired, brown eyes, rather a bitch?"

"That sounds like her. Joanna Champernoune," I said. We both laughed, struck by the folly and the fascination of discussing someone who had been dead for centuries as if we had met her at some party in our own time.

"She was arguing about manor lands," he said. "I did not follow it. Incidentally, have you noticed how one gets the sense of the conversation without conscious translation from the mediaeval French they seem to be speaking? That's the link again, between his brain and ours. If we saw it before us in print, old English or Norman-French or Cornish, we shouldn't understand a word."

"You're right," I said. "It hadn't struck me. Magnus—"

"Yes?"

"I'm still a bit bothered about side-effects. What I mean is, thank God I had no nausea or vertigo today, but on the contrary a tremendous sense of elation, and I must have broken the speed-limit several times driving home."

He did not reply at once, and when he did his tone was guarded. "That's one of the things," he said, "one of the reasons we have to test the drug. It could be addictive."

"What do you mean exactly, addictive?"

"What I say. Not just the fascination of the experience itself; which we both know nobody else has tried, but the stimulation to the part of the brain affected. And I've warned you before of the possible physical dangers — being run over, that sort of thing. You must appreciate that part of the brain is shut off when you're under the influence of the drug. The functional part still controls your movements, rather as one can drive with a high percentage of alcohol in the blood and not have an accident, but the danger is always present, and there doesn't appear to be a warning system between one part of the brain and another. There may be. There may not. All this is part of what I have to find out."

"Yes," I said. "Yes, I see." I felt rather deflated. The sense of exhilaration which 1 had experienced while driving back had certainly been unusual. "I'd better lay off," I said, "give it a miss, unless the circumstances are absolutely right."

Again he paused before he answered. "That's up to you," he said. "You must judge for yourself. Any more questions? I'm dining out."

Any more questions… A dozen, twenty. But I should think of them all when he had rung off. "Yes," I said. "Did you know before you took your first trip that Roger had once lived here in this house?"

"Absolutely not," he replied. "Mother used to talk about the Bakers of the seventeenth century, and the Rashleighs who followed them. We knew nothing about their predecessors, although my father had a vague idea that the foundations went back to the fourteenth century; I don't know who told him."

"Is that why you converted the old laundry into Bluebeard's chamber?"

"No, it just seemed a suitable place, and the cloam oven is rather fun. It retains the heat if you light the fire, and I can keep liquids there at a high temperature while I'm working at something else alongside. Perfect atmosphere. Nothing sinister about it. Don't run away with the idea that this experiment is some sort of a ghost-hunt, dear boy. We're not conjuring spirits from the vasty deep."

"No, I realise that," I sald.

"To reduce it to its lowest level, if you sit in an armchair watching some old movie on television, the characters don't pop out of the screen to haunt you, although many of the actors are dead. It's not so very different from what you were up to this afternoon. Our guide Roger and his friends were living once, but are well and truly laid today."

I knew what he meant, but it was not as simple as that. The implications went deeper, and the impact too; the sensation was not so much that of witnessing their world as of taking part in it.

"I wish", I said, "we knew more about our guide. I dare-say I can dig up the others in the Saint Austell library — I've found the Carminowes already, as I told you, John, and his brother Oliver, and Oliver's wife Isolda — but a steward called Roger is rather a long shot, and is hardly likely to figure in any pedigree."

"Probably not, but you can never tell. One of my students has a buddy who works in the Public Record Office and the British Museum, and I've got the business in hand. I haven't told him why I am interested, just that I want a list of taxpayers in the parish of Tywardreath in the fourteenth century. He should be able to find it, I gather, in the Lay Subsidy Roll for 1327, which must be pretty near the period we want. If something turns up I'll let you know. Any news of Vita?"

"None."

"Pity you didn't arrange to fly the boys over to her in New York," he said.

"Too damned expensive. Besides, that would have meant I had to go too."

"Well, keep them all at bay for as long as you can. Say something has gone wrong with the drains — that will daunt her."

"Nothing daunts Vita," I told him. "She'd bring some plumbing expert down from the American Embassy."

"Well, press on before she arrives. And while I think of it, you know the sample marked B in the lab, alongside the A solution you're using?"

"Yes."

"Pack it carefully and send it up to me. I want to put it under test."

"Then you are going to try it out in London?"

"Not on myself, on a healthy young monkey. He won't see his mediaeval forebears, but he might get the staggers. Goodbye." Magnus had hung up on me again in his usual brusque fashion, leaving me with the inevitable sense of depletion. It was always so, whenever we met and talked, or spent an evening together. First the stimulation, sparks flying and the moments speeding by, then suddenly he would be gone, hailing a taxi and disappearing — not to be seen again for several weeks — while I wandered aimlessly back to my own fiat.

"And how was your Professor?" Vita would ask in the ironic, rather mocking tone she assumed when I had passed an evening in Magnus's company, an emphasis on the 'your', which never failed to sting.

"In the usual form," I would answer. "Full of wild ideas I find amusing."

"Glad you had fun," was the reaction, but with a biting edge that implied the reverse of pleasure. She told me once, after a somewhat longer session than usual, when I had come home rather high about 2 a.m., that Magnus sapped me, and that when I returned to her I looked like a pricked balloon.