Either he had explored the house more systematically than I had had the opportunity of doing or he had stayed there before. Instead of heading for the main stairs he turned in the opposite direction. We had to pass several of the bedrooms, including Mary’s, and if I had not reached a state of total emotional paralysis I would have dropped in my tracks when I heard a crash and an inarticulate shriek from her room. The cry had been one of rage. She must be relieving her feelings by smashing lamps, vases, and other fragile objects.

John’s long, even stride didn’t alter. He was moving more easily now. The end of the corridor was in shadow, there were no wall sconces near it. What I had taken to be a dead end turned out to be a door, painted the same neutral colour as the wall. When he opened it I saw a landing with narrow, uncarpeted steps leading down, and another flight going up. It was lighted by a single bulb on the ceiling. I ought to have known there would be a separate staircase for the servants. Not that the knowledge would have helped. There would be people in that part of the house too.

I felt somewhat easier after John had closed the door, but when he sat down on the topmost step I said nervously, ‘What are you waiting for? The servants will be coming this way.’

‘No, they won’t. Not for a while.’ leaning back, supporting his weight on his elbows, he went on in the same subdued voice, ‘It’s obvious that you have never seriously contemplated a career in crime. If you do, bear in mind that strict attention to schedules is vitally important. Human beings are creatures of habit, and the older they get, the more they insist on regularity. Blenkiron always dines at seven-fifteen. The servants will be preparing dinner for the guests and eating their own; they don’t come upstairs to turn down the beds and so on until the guests have retired to – ’

‘John, if you don’t stop lecturing and start answering questions I am going to scream.’

‘Ask a sensible question, then.’

‘How did you get involved with – ’

‘No, no. That is a reasonable question, I admit, but under the present circumstances it is less relevant than a number of others, and the answer would involve a prolonged explanation which you probably wouldn’t believe anyhow. Try again, keeping in mind that our primary concern at this moment – ’

‘All right! Are we going to stay here until eight o’clock?’

‘What time is it?’

‘Seven-fifteen.’

‘How time flies when one is enjoying oneself,’ John murmured. ‘For the next half hour this is as safe a place as any. I’ve a little errand to do before we leave. You wait here while I – ’

‘No.’

‘It may be a bit tricky – ’

‘No. I’m not letting you out of my sight.’