And when I looked again, there wasn’t.

It gave me a thrill of accomplishment, knowing I’d managed to control it that time. Maybe that was all it took, a short pause to remind myself that I was only seeing things. At least I would be able then to muddle through until I’d had a chance to see a doctor.

On the desk a small brass carriage clock whirred briefly and began to chime the hours: Five o’clock. The others would be coming in quite soon, I thought, which meant I should stop sitting here and try to make myself a bit more useful to my hosts by going down and finding something I could cook them all for supper.

I stood and reached to switch off the computer, but before my hand made contact, the entire desk and what was on it wavered out of focus with the room, and then dissolved.

I closed my eyes again, more firmly this time, fighting back with all I had. I heard the window rattling as though from a blast of wind, and felt a brightening of light against my eyelids that surprised me into opening my eyes.

The door connecting with the spare room next to this one was now open, too, and framed within it stood the man in brown.

At least, the man who had been wearing brown, the last time I’d imagined him. This time, in place of the jacket, he wore a wine-red dressing gown that hung unfastened so that I could see he was still fully dressed beneath it in the plain white shirt and trousers and tall boots. It should have made him less imposing, but it didn’t. With the door frame for a reference he looked taller to me here. He’d have been six foot something, easily. His shoulders blocked the open space. He didn’t smile.

His voice was low and quiet, carefully controlled. ‘What are you?’

I was thinking just how odd a question that was for my own hallucination to be asking when his right arm shifted slightly and I saw what he was holding in his hand. I saw the knife.

It was a dagger, small and neatly made, and fit his hand so well I only really saw the blade, but that was all it took to make me feel a twinge of fear. Irrational, I knew, because this man was my creation, my own mind had called him up from somewhere, and as all the articles had said, he would be harmless. But I started to retreat, to back away as I had done before when we had faced each other on the hillside, hoping it would have the same effect. It didn’t. This time, instead of disappearing, he came after me and in two strides had crossed the room to take a firm hold of my arm with his free hand.

If the contact was a shock to me it seemed to shock him more, as though he’d been expecting that his hand would pass right through me. I was much too stunned to struggle, and besides, there was no point. His grip was far too strong, and he was far too close.

He asked again, as though the answer mattered even more, ‘What are you?’

Trying to remember the advice that had been in the final article I’d read, I met his gaze with all the calmness I could muster, and replied, ‘I’m real. And you are not. Now, go away.’

The dressing gown he’d worn was made of heavy silk, with hand-stitched seams. I knew this because he had shrugged it off a moment earlier and given it to me, with the excuse that my own clothes appeared ‘ill-suited to the weather’. It did, in fact, feel cooler in the room than it had felt before, and more damp, and the dressing gown, although it was imaginary, seemed to make a difference, so I thanked him.

After all, I reasoned, if I had to sit here with my own hallucination, who was acting like a gentleman, I could at least be courteous. I knew the situation would correct itself in time, and for the moment it was nothing short of fascinating.

Smoothing a fold of the dressing gown, I let the weight of the dark-red silk slip through my fingers and marvelled again at the power the mind had to make things seem real. It was one thing to read a psychiatrist’s paper on how hallucinations could deceive a person’s senses. It was quite another thing to wear a dressing gown that wasn’t there – to feel the fabric plainly in my hand, and see the little imperfections in the stitches of the sleeve.

Even the chair I was sitting in couldn’t be real, but I felt every bump of its low slatted back. There were two chairs, with curving arms, set facing one another by the window in this room that, while a vastly altered rendering of Uncle George’s study, still appeared to be a masculine retreat. Between the two chairs was a little table of dark wood that held a tray of pipes for smoking, one of which sat on its own and clearly was a favourite. There were no shelves for books but there were books stacked on the one free-standing cabinet that appeared to have a locking door, and books again at one end of the long and narrow table set against the wall, and on the table was a bottle that the man was lifting now to fill a pewter cup with something that both looked and smelt like brandy.

‘I’m not going to faint,’ I promised as he set it on the table.

‘I did not imagine that you were.’ He took the other chair and with one elbow on the table tipped the bottle over his own cup. ‘But it is clear your health has been affected by the shock of your arrival, and you would be wise to guard it.’

‘I haven’t arrived anywhere,’ I corrected him. ‘You’re the one who keeps turning up, and you’re not even real.’

‘Am I not?’

I hadn’t yet adjusted to the difference that a smile made to his face. I’d been too overwhelmed before to take much notice of his looks, beyond the broader details, but now that I’d relaxed more I was very much aware he was a very handsome man, for an illusion. His hair was not plain brown, but brown with glints of gold that caught the light. Close up, I now could see that his light-coloured eyes were green, so clear that at some angles they appeared transparent, and beneath the roughness of a day-old growth of beard his cheek and jaw were shaped with strength. A handsome man. But when he smiled he bordered on the irresistible.