‘EEG stands for “electroencephalogram”. In our work at the Baird Neurological Research Institute we find it helps in diagnosis to attach electrodes to the scalp and record on a moving strip of paper the patterns of electrical activity in the brain. Now in recent years we have also recognized that as well as the normal everyday conscious state, there are others.’

‘But I thought you were either conscious or unconscious,’ Carol interposed. Bourne did not bother to hide his annoyance at being interrupted in mid-lecture by such a fatuous remark.

‘No, no. That is a gross over-simplification of the truth. There is everyday consciousness, the mystic state, the hypnotic state, the hypnagogic and hypnopompic, and so on. Anyway, I was engaged in studying the degree of correlation of EEG patterns with various altered states of consciousness. At this particular part of the work I was using three good hypnotic subjects. One part of the technique was to regress the subject in age and see whether there were any interesting changes in his EEG trace. There were not but something else emerged.’

‘When Dr Bourne stayed with us on Mull,’ Meredith chipped in, ‘we were just beginning to consider the same sort of phenomena. Dr Bourne remembered this and very kindly invited me to visit him in Bristol to observe his subject. I was able to dig out a lot of the necessary background material, the history of Ardvreck House and so on. When I realized that much of its history came within the province of psychical research my interest deepened. I made enquiries and found to my dismay that the house was due for demolition and that we would have to hurry if we wished to do anything about it.’

Do what, for heaven’s sake? Paul asked himself in exasperation.

‘The owner was willing to give us permission to come over here and stay as long as we liked. He of course warned us of the state of the property, how it had lain unoccupied for fifteen years. But Dr Bourne, Mr Hunt and I felt it was worth while to set up this operation, especially since it was the last chance anyone would have of ever staying in Ardvreck House again.’

He glanced at his watch.

‘Look, it’s ten to three. In order to avoid long and lengthy explanations, let’s adjourn to the sitting-room. Mr Hunt and his people have been busy, I hope, and will be almost ready for us. Dishes can wait.’

Paul thought that both men, so dissimilar that they constantly irked each other, were at least united in their eagerness to begin. What? He and Carol followed Meredith out of the dining-room, across the cold hall, so dim it seemed to be lit by sunlight filtered through deep water, and into the lounge. Bourne, Smith and Pollard brought up the rear.