I stood perfectly still. The pattern was perfect. Whoever had walked across the courtyard had done so purposefully, with neat, even steps. I thought of the shuffling, shambolic Mr Parker, dragging his leg behind him. Thought of his wife. Her feet were surely too small. Could it be Christopher? Surely he would be back in London by now, squatting at the centre of his twisted web of lies, spies and secrets.

I took a step towards the window and peered through the glass, hoping I could work out who the steps belonged to by examining the shoes within. I saw only a further array of wellingtons and a stand for umbrellas into which somebody had deposited a dozen different walking sticks and a gaudy brolly.

Before I had even realized it, I was following the footsteps. I wasn’t sure whether to walk beside the prints or on top of them but as I looked back at my own steps I realized there was no way of disguising my presence here. And besides, it suddenly seemed important to me that I preserve the prints. I would need to show them to somebody later. I would need to photograph them. I would need plaster casts made for comparison against the prints that were still a dark stain against the wooden floor of my bedroom.

Should I have gone straight for Sergeant Chivers? Should I have gone home and called the exchange and demanded to be put through to the first available police officer? Should I have run down the hill to Felicity and John, or stood still and shouted Heron’s name until he came to my aid. Probably, yes. But I was a stubborn thing and it seemed absurdly important that I do this by myself. I needed to know. Needed to see if I had been the worst kind of fool.

The footsteps sloped gently upwards towards the nearest field. To my left were outbuildings with big open doors and high roofs. The floor was muddy and the space had been sectioned off into what looked, to my inexpert eyes, like individual cells. I passed them by. There was a tight feeling in my chest and I was gripping the wine tight in my right hand as I walked – the knuckles turning white against the green of the bottle and the deep red of the liquid.

The footsteps carried on past the metal gate that marked the entrance to the field. They doubled-back slightly. Whoever had made them had opened the gate and then retreated back into the courtyard as they swung it open. There was a small area of smudging and mess and then the steps carried on, across the field, where I could make out the shape of a small stone building with a brick roof.